IS-T 1777

Synthesis and Study of Conjugated Polymers Containing Di- or Triphenylamine

RECEIVED

by

Sukwattanasinitt, M.

AUG 2 2 19S6 OSTI

PHD Thesis submitted to Iowa State University

Ames Laboratory, U.S. DOE Iowa State University Ames, Iowa 50011

Date Transmitted: June 21, 1996

PREPARED FOR THE U.S. DEPARTMENT OF ENERGY UNDER CONTRACT NO. W-7405-Eng-82.

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iv

TABLE OF CONTENTS

GENERAL INTRODUCTION 1

PART I SYNTHESIS, CHARACTERIZATION AND ELECTRONIC 2 PROPERTIES OFN-INTERRUPTED CONJUGATED POLYMERS .

INTRODUCTION 3 RESULTS AND DISCUSSION 20 EXPERIMENTAL 68

PARTE REACTION OF ELECTRON-RICH ACETYLENES WITH 97 TETRACYANOETHYLENE

INTRODUCTION 98 RESULTS AND DISCUSSION 108 EXPERIMENTAL 154

CONCLUSIONS 175

REFERENCES 177

ACKNOWLEDGMENTS 189

1

GENERAL INTRODUCTION

This thesis consists of two separate parts. The first part addresses? the synthesis and

study of conjugated polymers containing di- or triphenylamine. Two types of polymers: linear

polymers and dendrimers, were synthesized. The polymers were characterized by NMR, IR,

UV, GPC, TGA and DSC. Electronic and optical properties of the polymers were studied

through the conductivity measurements and excitation-emisson spectra. The second part of

this thesis deals with a reaction of electron-rich acetylenes with TCNE. The discovery of the

reaction from charge transfer complex studies and the investigation of this reaction on various

electron-rich acetylenes are presented.

2

PARTI

SYNTHESIS, CHARACTERIZATION AND ELECTRONIC

PROPERTIES OF N-INTERRUPTED CONJUGATED POLYMERS

3

INTRODUCTION

Introductory Remarks

As part of a steadily growing interest in the electronic properties of organic materials,

a number of intriguing electronic properties and possible applications of arylamine compounds

have been discovered. Phenylamines are interesting in their own right because of their charge

transporting properties.1,2 Polymers containing these moieties are even more attractive as the

polymers would be more readily processable and provide better mechanical properties. A

number of non-conjugated polymers of di- and triphenylamine have been synthesized and used

effectively as hole transporting materials21' in organic electroluminescent devices. Conjugated

polymers containing diphenylamine and triphenylamine are rare. Polyaniline is the only well

known example of a conjugated diphenylamine polymer due to its high electrical conductivity

and environmental stability in the doped state. After extensive literature searches, we found

that no well-characterized diphenylamine and triphenylamine conjugated polymers, besides

derivatives of polyaniline, have been synthesized or studied. In this chapter of the thesis,

syntheses, characterizations, and preliminary studies of a series of conjugated polymers

containing diphenylamine and triphenylamine will be discussed.

Conjugated Polymers

Conjugated polymers are polymers which contain overlapping p-orbitals throughout

the polymer chain. Three types of p-orbital providing units have been used to construct

conjugated polymers: aromatic segments, non-aromatic segments andhetero atoms.

4a

Arrangements of these units in the polymer chains can be used to classify most of the currently

known conjugated polymers into five groups (Figure 1). Polyacetylene (PA)3,4 and

polydiacetylene (PDA)3d,s consist solely of conjugated double bonds or triple bonds.

Polyparaphenylene (ppp)3b-6 andpolythiophene (PT)3a-3b-3d'7 consist of conjugated aromatic

rings. Examples of copolymers of aromatic and non-aromatic segments are

polyparaphenylenevinylene (PPV)3'8 andpolyparaphenyleneethynylene (PPE).9 Polyaniline

(PANT)3 andpolyphenylenesulfide (PPS)3b are examples of polymers with alternating benzene

ring and hetero atoms. The last class is the polyacenes10 which consist of fused aromatic

rings.

Conjugated polymers are often capable of being doped, through chemical (or

electrochemical) oxidation or reduction, to states of higher electrical conductivity.3,4 The very

first synthesis and study of conducting polymers involved PA and PANI. Oxidatively doped

trans-PA is the most conductive (a = 103-105 S cm"1)11 among conducting polymers.

However, due to its poor environmental stabilities, PA is still only of academic interest. As an

environmentally stable material, doped PANI which possesses a lower conductivity (a = 1-

100 S cm'1)12 has been developed to the point of being a commercialized conducting polymer.

Other examples of conducting polymers are PT, PPP and PPV.

Even though electrical conductivity was the initial interest in conjugated polymers,

presently the underlying chemistry and physics of these materials in their undoped state seem

to be even more interesting. A number of new conjugated polymers have been synthesized

and studied in the past two decades. In 1990, physicists and chemists from the University of

Cambridge reported the first observation of electioluminescence from polymeric devices.13

4b

Type Representation Example

non-aromatic n polyacetylene3'^ polydiacetylene3"'5

n r\ r\

n -n - - -n

polyphenylene3^ *> polythiophene3a'3b>3c*»7

m non-aromatic h i J n

J n polyphenylene-polyphenylenevinylene3'^ ethynylene^

rv aromatic)—x-n

H X-k-

J n

r\ J n

polyaniline3 polyphenylenesulfide313

V J n

polyacenelO

Figure 1 Illustration of various types of conjugated polymers.

The device was constructed sandwiched between indium tin oxide (TTO) and aluminum

electrodes. Conjugated polymers have also been studied for nonlinear optical properties,

magnetism, photoconductivity, chromism, and sensoring.3 Relationships between the

structure of polymers and their properties are always of great interest

This dissertation involves the synthesis and studies of nitrogen containing polymers

whose structures are closely related to PANI, PPV and PPE. The following sections are thus

devoted to the discussion of these polymers in more detail.

Polyaniline and Its Conductivity

Polyaniline (PANI) was known long before its current interest as aniline blacks which

are undesirable black deposits formed on the anode in electrolyses involving aniline. Recent

studies of polyaniline have shown that the polymer can exist in a wide range of structures

depending on the environment14 Under basic conditions, the polymer has the generalized '

composition consisting of amine and imine repeating units as shown below.

The oxidation state of the polymer is determined by 1-y which can be varied from 0 to 1. The

fully reduced form, (1-y) = 0, is called 'leucoemeraldine', the half oxidized form, (1-y) = 0.5 is

called 'emeraldine' and the fully oxidized form, (1-y) = 1 is called 'pernigraniline'. The imine

nitrogen atoms can be protonated in whole or in part to give the corresponding salts (Scheme

1). The degree of protonation of the polymeric base depends on its oxidation state and on the

pH. A complete protonation of imine nitrogen atoms in emeraldine base by aqueous HCl, for

example, results in the formation of emeraldine hydrochloride salt which has a conductivity

about 9 to 10 orders of magnitude higher. This fully protonated emeraldine salt is the most

highly conductive form of polyaniline.12

- 0~HI)hN~0~iKI)~i1*' ■ leucoemeridine

+ 2e" -2e"

emeridine salt

+ 2e" -2e"

emeridine

+ 2e" -2e"

/=\ ¥e/=\ ?s ¥©/=\ ¥a

fully protonated perigraniline

•2HH

2H +

half protonated pernigraniline salt E

2H+ I -2H +

- -0~N=0=N_0"Ni=0=N" pernigraniline

Scheme 1

If the emeraldine salt had the above cationic bipolaron constitution as shown in

Scheme 1, it would be diamagnetic. However, extensive magnetic studies have shown that it

is strongly paramagnetic and that its Pauli (temperature-independent) magnetic susceptibility

increases linearly with the extent of protonation.14 These observations and earlier studies15

showed that the protonated polymer is actually a delocalized polysemiquinone radical cation,

one resonance form consisting of two separated polarons:

7

H

^"-Xj^rsj-^-xj-?: H'

n

Polyaniline is a special conducting polymer in that its most highly conducting doped

form, emeraldine salt, can be reached by two completely different processes, protonic acid

doping and oxidative doping (Scheme 2). For example, emeraldine hydrochloride salt can be

obtained from the addition of 1M hydrochloric acid to emeraldine base or from the oxidation

of leucoemeraldine by chlorine gas.

H _ H N-

I emeraldine o-=10-10Scm-1

n HCl

H i > H j > H , > H N-

cr a,

\J^"-Vjt£-Yjtn-VjtS-a"

emeraldine hydrochloridi a = l - 5 S c m - 1

n

H t

H H

^ ^ N - \ \ /r™-\ /rN-\ /r"- . - K H W H

leucoemeraldine

J n

Scheme 2

Alkyl derivatives of polyaniline were also synthesized in order to improve the solubility

of the polymers in common organic solvents. Poly(N-alkylanilines)16 andpolyalkylaniline17

were prepared from either chemical oxidative polymerization or electrochemical oxidative

polymerization of N-alkylanilines and o-alkylanilines (or m-alkylanilines).

8

R N-

-■n Poly(N-alkylaniline) Poly(alkylaniline)

The conductivity studies showed that doped poly(N-alkylanilines) have conductivities of 10"7-

10"6 S cm"1 and doped poly(alkylaniline) have conductivities of 0.3-1 S cm"1.

Although the radical cations of arylamines are known to be especially stable,

polyaniline is the only conjugated polymer containing diphenylamine units which has been

extensively studied. Only a few synthetic attempts for other conjugated polymers containing

diphenylamine have been reported. In 1989, electropolymerizations of 4-aminobiphenyl and

diphenylamine were reported (Scheme 3).18 The resulting insoluble film from both

polymerizations was proposed to be poly(4-phenylaniline) based on IR.

O-O-1^30" MeCN V //~\ //

Scheme 3

H •N-

HC1,E°

-Jn MeCN O-S-O

The nonlinear optical properties of this polymer were studied and the third-order nonlinear

susceptibility, %(3), of 1.3 x 10"10 esu was reported.19

Triphenylamine conjugated polymers were synthesized in 1991 by Ni-catalyzed

coupling polymerization.20 The polymerization of 4,4\4"-Mbromotxiphenylarriine yielded an

insoluble network polymer and the polymerization of 4,4'-dicMorotriphenylarnine yielded a

low molecular weight (Mw = 2500-3000) linear polymer (Scheme 4).

3/2 Mg Ni(bpy)Cl2

BrI7 XX » Mg Ni(bpy)Cl2

cr ^ ^ THF

CI xrtx Scheme 4

The proposed structures of the polymers were based on IR and elemental analysis. A film of

these polymers were doped by I2 vapor to reach a maximum conductivity of 0.7-1.2 S cm"1

after an 18 h exposure period. An electrochemical study indicated that the maximum

conductivity corresponded to a 50% doping level.

Polyparaphenylenevinylene and Light Emitting Diodes

Unlike polyacetylene and polyaniline, polyparaphenylenevinylene (PPV) is a strongly

photoluminescent conjugated polymer. The current interest in PPV focuses upon its

photophysics and opto-electronic applications. Following the first observation of

electroluminescence (EL) of the polymer-based LED constructed from PPV,13 a number of

PPV derivatives have been synthesized. With an introduction of an alkoxy chain, poly (2-

methoxy, 5-(2'-ethylhexoxy)-l,4-phenylenevinylene, MEH-PPV, is soluble in organic solvent

that greatly simplifies the fabrication.21

10

MEH-PPV

A device constructed from MEH-PPV also emits light at longer wavelengths than that of the

PPV device due to the smaller energy gap between HOMO and LUMO produced by the

electron donating alkoxy groups.

There are a number of advantages of the polymer-based LEDs: low cost, simple

fabrication, the possibility of color tuning through rational structural designs,22 the

accessibility to large area devices, and flexible LEDs.23 An example of a flexible LED

consisting of poly(ethylene pthalate) (PET) as a substrate, conducting PANI as a hole injector,

MEH-PPV as an emissive layer and calcium, Ca, as an electron injector is shown in Figure 2.

Figure 2 A flexible LED

11

Currently, research in the area of polymer-based LEDs is focused on the improvement

of environmental stabilities and EL quantum efficiencies, T|+, of the devices. In order to

achieve this, mechanisms of the electroluminescence must be understood. There are at least

four steps involved in electroluminescence: charge injection, charge transport, charge

recombination, and light emission (Figure 3).3c

v_7*ii$2] YjiccurrjL.Ley.eL

holejurjectoij'''' fluorescent polymer (PPV) (ITO)

$ .

elBl electron injectoi

(Ca)

Figure 3 Schematic EL process in a V volts forward biased LED constructed from PPV, ITO

with work function of <&i and Ca with work function of <E>2.

Charge injection consists of two processes occurring at both interfaces of the

fluorescent polymer layer: (1) electron injection from an electron injector to the fluorescent

polymer, and (2) hole injection from a hole injector to the fluorescent polymer. An electron

injector is usually a low ionization energy (work function, <£2) metal such as Ca and Al. A

hole injector is usually a high ionization energy (3>i) conductor such as indium tin oxide (ITO)

and conducting PANI. According to Figure 3, the lower the energy barrier between the Fermi

level of the hole injector and HOMO of the polymer the easier the holes can be injected. A

• 12

lower barrier between the Fermi level of the electron injector and LUMO of the polymer

allows for easier electron injection. The efficiency of the hole injection is thus dependent upon

the difference between the ionization energy of the polymer and the work function of the hole

injector (I-3>i). The efficiency of electron injection is dependent upon the difference of the

work function of the electron injector and electron affinity EA of the polymer (<£>2-I).8 These

two values, (I-<&i) and (<52-I), can be varied by changing the metal electrodes or structural

design of the fluorescent polymers.

Charge transport in the fluorescent polymer film is accomplished through two types of

carriers: (1) electrons carrying negative charges and (2) holes carrying positive charges. In

most conjugated polymers including PPV, the mobility of holes is faster than the mobility of

electrons.8 The differences in mobilities cause an unbalanced charge in the polymer film and

the charge recombinations occur close to or inside the negative electrode. If the

recombinations occur close to the negative electrode, the EL quantum efficiency is diininished

by the self-absorption. The recombinations inside the metal electrode give no radiative decay.

The low quantum efficiency caused by this unbalanced charge transport can be improved by

adding an electron-transporting layer25 between the polymer and electron injector or by

blending an electron transporting material with the polymer.22b'26 Hole-transporting

materials1,2 such as arylamines have also been used to improve the EL efficiencies in polymer-

based blue LEDs22a,b'27.

Charge recombinations in a fluorescent polymer yield excitons when traveling holes

and traveling electrons meet (Figure 3). The recombinations of electrons and holes are

random in mutiplicities. Statistically, only one fourth of the excitons are singlet excitons

13

which are responsible for the EL. The maximum quantum efficiency of the EL would thus be

about one-fourth of the PL. As mentioned earlier, the positions of the charges recombinations

depend on the mobilities of the carriers. The charge recombinations are useful only when they

occur in the polymer film and the emitted light will have a greater chance to be observed if the

recombinations occur closer to the transparent electrode.

Light emission in EL is derived mainly from radiative decay of singlet excitons, as in

PL, after the charge recombinations. The theory on structure-fluorescence dependence has

not been conclusive and is still a topic of great debate.28 However a few mechanisms83

responsible for non-radiative decay are well-known in organic solids. Intersystem crossing

from singlet to triplet, exciton-exciton fusion at high excitation densities, and exciton

migration to quenching sites are all mechanisms which affect the photoluminescent quantum

yield of PPV. The last mechanism, exciton migration, accouts for the lower quantum yields of

longer conjugated PPVs compared to the shorter ones.29 The PL quantum yields of PPV and

its derivatives are 5-25% while the PL quantum yields of the corresponding dimers, stilbenes,

are 90-100%. An improvement of EL quantum efficiency was also observed when PPV was

replaced by a partial conjugated PPV.22d

The EL quantum efficiency Cn ) can be described in terms of the double charge

injection factor (y), efficiency of production of a singlet excitation from a hole-electron pair

(T|r), and the quantum efficiency of fluorescence (<j)f), as shown in the equation below:2"

%=ynr«{)f

This equation indicates that the high quantum efficiency requires efficient injections of both

carriers as well as hole-electron recombination leading to a singlet exciton, and high

14

fluorescence quantum yield.

Environmental stability of the polymers is another consideration in developing a new

polymer-based LED. There are two recognized sources, from electron injecting metal and

emissive polymer layer, responsible for instability of the polymer-based LEDs. A good

electron injector such as Ca is usually not stable to 02 oxidation. Using a more stable metal is

one solution but this also poses other problems such as lower EL quantum efficiency and a

higher threshold voltages. The higher threshold voltages can cause damage to the polymer

layer through electrochemical reactions and local heat The design and synthesis of new

electrochemically stable polymers which have an ionization energy and electron affinity

matching the work functions of the electrodes are thus extremely important

The synthesis of PPV and related stilbenoid compounds were recently reviewed.9,30

Therefore, only a list of polymerization reactions and references of recent syntheses are given

below.

Heck reaction polymerization:31

15

Precursor Route (Wessling Reaction) ,22d,32

XCHJ-4 ^ - c i y c NaOH CHX

®/—\^e -X: -CI, -Br, -OCH3, ^ ( C H g ^ c f - S ^ j C r ? - ^ ) ^ J n

Wittig reaction polymerization:

X

.33a,b

/ = \ P /=( PPh3+Br"

0r^J^:y^x)-J

McMurry reaction and ring-opening metathesis polymerizations were also reported for the

synthesis of PPV and its derivatives.330

Polyphenyleneethynylene

PPE and PPV are very similar in their structures with the only difference being that

PPE has a triple bond, while PPV has a double bond, as a bridge between two phenylene

rings. Both polymers also possess many similar properties but with different merits. Studies

of the PPE system started over a decade after the PPV system. Studies of PPE systems have

developed slowly due to synthetic inaccessibility of processable PPE polymers.

The syntheses of PPE and its derivatives were recently reviewed9'34 and will not be

discussed here. This section will focus on the opto-electronic properties of the conjugated

16

phenyleneethynylene (PE) system with some comparisons with thephenylenevinylene (PV)

system. The progress in recent applications and chemistry in the conjugated PE system will

also be surveyed.

Electron derealizations through a triple bond in PE and a double bond in PV were

compared theoretically and experimentally. Some evidence indicates that the double bond

allows better electron delocalization than the triple bond. The direct observation is that the

wavelengths of electronic absorption maxima ( max) of the PE compounds are shorter than

that of the PV analogues.

P c iAs

^12^25 J n A,max(THF)=425nm34

Me,

A.max(CHCL) = 415nm35

Tnaxvvl l"3'

OC12H25

Ajnax(CHCl3)=45?nm31b

,N—ff \—=—/ V-N02 Me2N

Xmq„(CHCL) = 430 nm3* Tnax^ ^ 3

1 A.max(CHCl3) = 322nm36a Xmav(CHCL) = 356nm36b

vmaxvv'JL-l^i3

17

Indirect observations, such as the first hyperpolarizabilities (p), were also reported. The |3

values of PE derivatives are lower than those of the analogous PV derivatives,35 indicating the

lower molecular polarizabilities of the PE system.

Photoluminescent properties of PE derivatives and PV derivatives were studied.36 The

reported quantum yields of many of the PE derivatives are comparable to those of the PV

analogues. The quantum yield of alkoxy PPE in toluene37 was reported to be as high as 50%,

which is about two times higher than that of PPV. Despite being highly fluorescent studies of

electroluminescence of the PPE system have not yet shown satisfactory results9 compared to

the PPV system.

PPE and its derivatives are interesting due mainly to its unique rod-like structure. By

taking advantage of the rod-like structure of PPE, S wager38 was able to unambiguously

demonstrate an increase in sensitivity of fluorescent chemosensors based on energy migration.

The rod-like structure of PE-based molecules allows predictable geometries which are

important for molecular architecture in supramolecular chemistry and nanomolecular

chemistry.39 The PE units have been utilized as building blocks for the construction of defined

length molecular wires,40/precise size macrocylics,41 shape persistent organic lattices,42 and

defined shape dendrimers,43 for examples:

Et2N-N=N-14

a molecular wire consisting of 16 PE units with a molecular length of 128 A40

18

a rigid macrocycic consisting of 12 PE units with a diameter of 21 A41

a molecule which can from a shape persistent, zeolite-like, lattice

19

%k >V< V V

a dendrimer consisting of 58 PE units with a diameter of 85 A

20

RESULTS AND DISCUSSION

Linear conjugated polymers containing diphenylamines

Incorporating of diphenylamine units into a conjugated polymer chain forms N-

interrupted conjugated polymers consisting of all three types of conjugated segments, hetero

atom, aromatic, and non-aromatic segments. Rapresentation and examples of N-interrupted

conjugated polymers are shown in Figure 4.This class of polymers may possess the combined

properties of types I, II, HI and IV (see Figure 1) and/or other interesting properties.

non-aromatic -■n

examples: Jn

N-interrupted PPE N-interrupted PPV

Figure 4 Representation and examples of N-interrupted conjugated polymers.

The electronic and optical properties of acetylene-based polymers is an area of

considerable interest in our research group.9,44 Thus, diphenylamine was incorporated first

into PPE to give N-interrupted PPE.

C6H13

J n

Series of N-interrupted PPE l m = 0 l m = l , X = H 2 m = l , X = OC6H13

4 m = l , X = OC8Hn

21

A series of N-interrupted PPEs (1 ,2 ,3 and 4) were synthesized. A key monomer for

the synthesis of these N-interrupted PPE is 4,4'-diemynyl-N-hexyldiphenylamine, 8, which

was synthesized in four steps from diphenylamine (Scheme 5). Phase transfer N-alkylation45 of

diphenylamine with bromohexane yielded N-hexylamine, 5 in 82% yield. Double iodination46

C6H13Br C 6 H 13 2BTMAICL C 6 H 1 3

\=/ \=/Bu4NBr,Toluene\=/ >=/ CKf^ \=/ £ \=/ 5 MeOH

70uC,24h. (82%) 12h,(86%)

C 6 H 13

2 ^—SiMe 3 Pd(PPh3)Ci2 CuI.E^N Toluene 12 h. (100%)

KOH, MeOH

30min(91%)

C 6 H 1 3

Me3Si-2

-SMe,

Scheme 5

of 6 with a mild iodinating reagent, benzyltrimethylammonium chloroiodate (BTMAIC12),

gave diiodo compound 6 in 86% yield. Pd-coupling47 (100% yield) of 7 with two equivalents

of trimethylsilylacetylene followed by deprotection (91% yield) of the trimethylsilyl group

afforded the desired monomer 8. In our early attempts to synthesize polymer 1, a typical Pd-

coupling condition9, Ma was utilized to polymerize monomer 8 with monomer 6 (Scheme 6).

& + £

PdCl2(PPh3)2

Cul, EtjN

Toluene

96H13 r\ o 80-85%; Mn = 3 x 103-6 x 10:

Scheme 6

22

The polymerizations used 4% mole equivalents of PdCl2(PPh3)2 as a catalyst, 8% mole

equivalents of Cul as a co-catalyst (Sonogashira's catalyst system),478 and triemylamine as a

base and co-solvent, in toluene at room temperature or slightly elevated temperature (40-

50°C). After 24 h, polymer 1 was obtained in high yield (80-85%). The polymer however

possessed low molecular weight (Mn ~ 6.0 x 103, GPC against standard polystyrene),

corresponding to a degree of polymerization (DP) of 21. Neither the addition of more

catalysts during polymerization nor extending the reaction period improved the molecular

weight. Raising the reaction temperature above 50°C caused crosslinking resulting in low

yields of the soluble polymer. However, with an addition of two equivalents of a stronger

base, l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), the polymerization" (Scheme 7) appeared to

PdCl2(PPh3)2

Cul, DBU 3 + £ * -

EtjN, Toluene

96H13

_.<Q4_<Q, J n

94%;Mn = 3.09xl04

Scheme 7

proceed faster. Polymer 1 was obtained as a pale yellow fibrous solid in excellent yield

(94%). The molecular weight was about five times higher (3.09 x 104, DP = 111) than when

the polymerization was conducted in an absence of DBU.

It is known that electron-rich aromatic halides are not very reactive toward the Pd-

coupling reaction.47b Oxidative homo-coupling of two terminal acetylenes was reported to be

competitive with Pd-coupling of halides and acetylenes (Scheme 8).9,43a,b A stronger base

such as DBU presumably increases the rate of the hetero-coupling reaction between 8 and 6.

23

Ar-

Ar- -H

-H

oxidative homo-coupling

Ar-

Ar—I Ar-hetero-coupling

•Ar

-Ar

Scheme 8

This faster coupling results in the reduction of the homo-coupling, which leads to an improper

stoichiometric ratio of the acetylene and iodide and thus a low molecular weight polymer.

Polymers 2,3 and 4 (bright-yellow, fibrous solids) were obtained from the

polymerization of diethynyl monomer 8 with diiodo compounds 9,10 and 11 respectively

(Scheme 9). The polymerizations proceeded extremely well in the presence of two

equivalents of DBU as indicated by the yields (89-97%) and number average molecular

weights (> 1 x 104, Table 1). Polydispersities of the polymers were 1.70-3.07, which are

typical for step growth polymerizations. Polymerization in the presence of DBU at a lower

S + I

PdCl2(PPh3)2

Cul, DBU

Et3N, Toluene

C 6 H 13

H>—o— r\ 2 X = H !flX = OC6H13

U X = OC8Hn

2X = H(97%) 2X = OC6H13(93%) 4X = OC8H17(89%)

Scheme 9

24

Table 1 Number average molecular weight (M„), degree of polymerization (DP), weight

average molecular weight (Mw), polydispersity (PD), and intrmsic viscosity (TV) of polymers

1,2,3 and 4.

lymer

1

2

3

4

Mn

3.09 x 104

1.03 x 104

1.68 x 104

2.58 x 104

DP

111

55

57

81

Mw

5.24 xlO4

3.16 x 104

3.16 x 104

6.27 x 104

PD =MJMn

1.70

3.07

1.60

2.58

IV (dL/g)

0.63

0.96

0.62

0.38

amounts of the catalysts (2% PdCl2(PPh3)2/4% Cul) was also as effectivein the presence of

DBU. Two equivalents of DBU could also be utilized in the absence of triethylamine in the

polymerizations to give polymers with similar molecular weight

The degree of polymerization likely was controlled by the solubilities of the polymers.

Among these four polymers, polymer 2 was obtained in the lowest molecular weight because

its rigid structure limited its solubility. Despite possessing the lowest molecular weight,

polymer 2 had the highest intrinsic viscosity (0.96 dL/g) which again due to its rigidity. With

hexoxy and octoxy chains, polymers 3 and 4 possess higher molecular weights (1.68 x 104 and

2.58 x 104) and lower intrinsic viscosities (0.68 and 0.38 dL/g). The alkoxy chains increased

the flexibility of the polymer molecules as well as their solubilities. The solubilities of

polymers 1,3 and 4 were 35-40 mg/mL in toluene and about 100 mg/mL in THF which were

two to three times higher than that of polymer 2.

25

Structural assignment of the polymers was achieved by 2H and 13C-NMR. Figure 5

shows ^-NMR spectra of polymers 1 and 2 compared to that of diethynyl monomer 8. A

singlet signal of two protons on the terminal acetylenes of monomer 8 was absent in the

spectrum of the polymers, indicating that all the terminal acetylenes underwent a complete

coupling reaction. A small doublet signal at 7.7 ppm belongs to the aromatic protons of the

iodo monomer at the end of the polymer chains. The signal was more pronounced in polymer

2 than in polymer 1, supporting the GPC results of their relative molecular weights. The 13C-

NMR spectrum of monomer 8 contained two sp-C signals at 76.2 and 83.8 ppm

corresponding to the terminal acetylene carbon and the internal acetylene carbon, respectively

(Figure 6). For polymer 1, only one sp-C signal (at 88.8 ppm) was observed, corresponding

to symmetrical acetylenic carbons. In polymer 2, the two acetylene carbons were not

equivalent and they are observed at 88.5 and 91.5 ppm.

Diethynyl monomer 8 was also polymerized by oxidative homo-coupling48 to produce

diacetylene polymer 12 (Scheme 10). A high yield (86%) of polymer 12 with high molecular

weight (4.99 x 104) and low polydispersity (1.40) was obtained, demonstrating that electron-

rich diethynyl monomers are quite suitable for oxidative coupling polymerization.

The repeating unit of polymer 12 consisted of one more rigid acetylene unit than that

of polymer 1. However, the chain rigidities of these two polymers are apparently not much

different, as their solubilities and the intrinsic viscosities (0.78 dL/g for 12 and 0.63 dL/g for

1) are quite similar, especially when the difference in the molecular weights is taken into

account.

26

f

^

r

KJ

'

QH 1 3

l o^at

G>H13

8.

f

ftHl3

V.

■K>—O—O--n

- j — i — i — i , -

6 5 - i — ] — r -

4

A M

\J \ , v^y

AJ /L_

Figure 5 XH-NMR of polymer 1, polymer 2 and monomer 8 in CDQ3.

27

i

'tymi^^ i j 1 1 1 1 1 1 1 1 ' 1 1 1 1 1 1 1 1 1 1 j 1 1 — i i 1 1 1 1 , i

168 148 lee tee Bfl 1 1 1 I

as B p p .

U K ^■■^'^■■■■iiE^'fWH

&

!

MP

ii «■< una in inn i j jm i^ t iniinnnn ,ii n ■ rm'SmiiMi n i i i o i r ~n 'nnnwi i r r i - r r IITI*—iiY* T V " '1 ,

" i ' — •!* ■ r"*un T

! l! l»! I _ J | I I ij>*»ii»ii»S>ii»tM»wii»in»ii>*iw»m>WiW<«>H)iw>W'>wiiri'tffi«^wn>i>»y*i

Figure 6 13C-NMR of polymer 1, polymer 2 and monomer 8 in CDC13.

28

CuCl-TMEDA &

02,THF

C6H13

f-O -Or 86%, MJJ = 4.99 x 104, DP = 166 PD = 1.40, TV = 0.78 dL/g

Scheme 10

The chain-ended XH-NMR signals of polymer 12 at 6.7 and 7.1 ppm are almost

unnoticeable and no detectable chain-ended signal observed in 13C-NMR (Figure 7). This

confirms the high molecular weight of this polymer. The 13C-NMR signals at 73.6 and 81.9

ppm correspond to sp-carbons attached to the acetylene and the phenyl ring, respectively.

Ethynylene conjugated polymers containing carbazole, a well known hole transporting

molecule,1,2 were also synthesized. The key monomer, 3,6-diethynyl-N-octylcarbazole, 16

was synthesized in four steps (total yield = 51%) from carbazole through a reaction series

similar to that used in the synthesis of monomer 8 (Scheme 11). Double iodination of

carbazole was however required a stronger iodinating reagent, iodinemonochloride (IC1).

The Pd-coupling polymerization of monomer 16 with diiodo monomer 14 produced a

white polymer, 17, in 79% (Scheme 12). This polymerization was not as successful as the

polymerization of monomer 8, previously described, indicated by the lower yields and the

molecular weight distribution of this polymer. Polymer 17 has lower molecular weight (Mn =

1.19 x 104) and broader polydispersity (PD = 3.73, Table 2) than its diphenylamine analogue,

polymer 1. It was first assumed that the lower molecular weight and broader polydispersity

29

-•

vU a

u L

in nt o N n W •*> » ID (0

kM^

1 ' " ' l l l |H«IU M H A M M .

in ▼ u> to

U.U

• M A « l | « H I M l M l M M « f * « M H

' I ' ' ' ' 1 ' ' ' ' I ' ' ' ' I ' ' ' ' | ' ' ' ' I ' ' ' ' | ' 1 1 I | I I I I | I I 1 I | I I I I | I I I I 1 I 1 I I | I I 1 I | 1 I I I | 1

16* 140 1E9 100 t t B* 40 20 I ■ I I I I I ' ' ' I

0 ppa

Figure 7 a) XH-NMR and b) 13C-NMR of polymer 12 in CDC13

30

CgO I

H

CgH^Br KOH/K2C03

1 NBu4Br, Toluene reflux, 16 h (98%)

ie S ^ - N - ^ V ^ CH2Cl2,MeOH S ^ N ^ X ^

11

(90%) I CgH17

14

-SiMe,

M^Si

PdCl2(PPh3)2, Cul EtjN, Toluene (82%)

M&3

KOH

MeOH, i-PrOH (70%)

Scheme 11

were due to the low solubility of polymer 17 (about 10 mg/ mL toluene). An attempt to

increase the solubility and thus the molecular weight was done by incorporating the more

flexible segment, N-hexyldiphenylamine, into the ethynylenecarbazolene chain to form

copolymer 18. Even though this copolymer has higher solubility (about 20 mg/ mL toluene)

than polymer 17, the polymerization did not give a notably better result, as a polymer with M„

= 1.08 x 104 and PD = 3.41 (Table 2) was obtained in 84% yield. Due to the lower molecular

weights of polymers 17 and 18, the intrinsic viscosities of these polymers (0.21 and 0.24) are

also lower than that of polymer 1.

All the polymers, except for polymer 17, can be cast into flexible free-standing films

unlike poly-2,5-dialkoxyphenyleneethynylenes9 which form brittle films. The films remained

flexible over two years. The films cast from toluene solutions (10 mg/ mL - 30 mg/ mL) are

particularly homogeneous and transparent (Figure 8).

31

Ik

PdCl2(PPh3> Cul, DBU

Toluene C6H13

S B -O- N -0 - S

8H17

Scheme 12

Table 2 GPC results of polymers 17 and 18.

Polymer

12

1§

Mn

1.19 x 104

1.08 x 104

DP

38

42

Mw

4.43 x 104

3.70 x 104

PD =MW/Mn

3.73

3.41

IV (dL/g)

0.21

0.24

Thermal behaviors of these polymers were studied by Thermogravimetric Analysis

(TGA) and Differential Scanning C!alorimetric Analysis (DSC) under nitrogen atmosphere.

The TGA was performed from room temperature to 1100°C with a ramp of 20°C/min. All

polymers showed a single weight loss. Thermal degradation of polymers containing

diphenylamine (1,2,4,12) started (5% weight loss) at temperatures over 370°C (Table 3).

32

7TT--55v

CeHrj

i n

J i, i

•rS^E

* n

r^ / v-r~^/

- ' / - \

Figure 8 Photograph of free-standing films of polymers 1,2 and 24 shown actual sizes.

33

Table 3 TGA and DSC results of N-interrupted PPEs.

Polymer

1

2

3

4

U

XL

18

Temperature (°C) (% remaining weight)

410 (94)

383 (96)

373 (96)

386 (96)

423 (96)

287 (96)

343 (95)

TGA

%reniaining at 1100°C

53

60

44

40

58

51

55

weight

DSC

Qosslinking Temperature (°C)

225

254

270

273

195

224

178,231

The polymers containing carbazole were less withstanding to thermal degradation as

homopolymer 12 and copolymer 18 had 4-5% weight loss at 287°C and 343°C, respectively.

The DSC thermogram (Figure 9) indicated that all synthesized polymers did not melt before

an exothermic reaction, likely crosslinking, ocurred. Only broad and shallow endothermic

transitions were observed before the crosslinking temperature, presumably corresponding to

the sidechain softening. Small endothermic peaks at 50°-75°C were possibly due to

evaporations of trace solvents in polymer samples.

The electronic absorption spectra (Figure 10) of these polymers in THF were

recorded. Absorption peaks ( ma*) were determined and absorption edges (A*) were estimated

within ± 5 nm (Table 4). As expected, the X^ and 7^. increase with an increasing conjugation

34

: s : i w » » SOD » p 1#M***0IW0 C*Cl h n r i t » « . W Du** f i :

: f * » o ; H I M O w o *3o ; 0 M t * - 0 t w « I ' d t*w*«-0t t* t o A * * * * ;

...

.....

1 .

\ \ M

fiu

4

™ ^ /

3 . I M i s , m ZM vn Mo .oo

3 . 1.0 |5« 2.0 n o JO0

2

! ...

18

Figure 9 DSC thermograms of polymers 1,2,3,4,12,12 and 18.

35

400.n w.-ivolencitli (nm.)

55n .»

O.SOOOO-, - -

0.40000-

0. 30000-

0.20000-

o.ioooo-

0.0000-

/ -' \ \ / 3 \ 'i

_ / \ 1 2 ' \ »

300 400 URVELEHGTH

500

i

0.50000-,

0.40000-

0.30000-

0.20000-

0.10000-

p 250

1

300

a \ w 350 400

UnUELEllGTII 450

•

rno

Figure 10 Electronic absorption spectra of polymers 1,2,3,4,12 and 18 in THF.

36

Table 4 UV-Vis absorption maxima (A ax) and band edges (A*) of the N-interrupted polymers

in THF solution and their films.

THF solution Film Polymer

1 2 3 4

12

12 18

Amax(nm)

389 292,400

300,416

302,415

399 270, 316, 366

270, 314, 368

A*(nm)

430 445 455 455 450 395 415

Amax(nm)

390 296,408

298,420

304,408

417 250, 320,366

252, 322,372

A«(nm)

450 465 475 475 475 405 425

(compare A™* of polymer 1 with those of polymers 2, and 12). Electron-donating

substituents, in this case alkoxy groups, also increase the A ^ (compare A ^ of polymer 2

with those of polymers 3 and 4).

Surprisingly, polymer 12, despite having a through conjugation and a more planar

repeating unit, has a A x and A* shorter than that of polymer 1. Polymer 1 is not a through

conjugation and its repeating unit is not planar (Scheme 13). We have not produced a

satisfactory explanation for this contrary result The UV-Vis spectrum of copolymer 18

appears to be a spectram of polymer 17 modified by the spectrum of L The spectrum of 18

has the same three bands as that of 12 but the A* is about 20 nm longer (15 nm shorter than

37

N

C = C - -

%_J~7^%_J C6H13

n

C = C - -

J n

C=C=

0 % ^

C6H13

J n

C=C= =

Scheme 13

that of 1). The relative intensities of the three bands were also altered. The highest intensity

band in the spectrum of 18 is 368 nm, while in the spectrum of 12 it is 316 nm. Thus,

copolymers may be used to modify electronic absorption spectra.

The UV-Vis absorption of films of the polymers were also measured. Except for

polymer 12, the films of polymers have the same absorption peaks (Table 4) as their solutions.

The tails of absorption bands of the polymer films extended about 20 nm longer than when in

solution. The same Amax but with a longer tail suggests that the conformation of the

conjugated segments in the polymer chains in the film state are mostly the same when in

solution. A film of polymer 12 gave a A ^ which was 18 nm longer than when in solution,

which was previously observed in PPE.9,34b This implies that the conformation in the film

state allows better conjugation.

The structures of N-interrupted polymers are similar to the leucoemeraldine form of

polyaniline (see introduction section). Electrical conductivities of the polymers measured by

two in-line probes were lower than the equipment threshold (< 10"9 S cm"1). Oxidation of

38

these N-interrupted polymers by iodine should yield a polymer with a similar structure as the

conductive form of polyaniline, emeraldine salts (for example: Scheme 14). However, when

the polymers were doped by iodine vapor, only polymer! showed any conductivity at all, and

that was only a mere lO^-lO"6 S cm"1.

^6H13 ct<Pvi c

t<5Hi3 So-1*13 >—of Jn/4

C6H13

n/4

-*-\=r

c.^ii

X-f\.

- W " w -h

C.6H13

f~% k f \ ~

m\=r^\

C6H i3

-/ViL/

Scheme 14

During this conductivity study, a conductivity of the same order of magnitude was also

reported for poly(N-alkylaniline)16. The low conductivity of N-alkylated polymers such as our

N-interrupted conjugated polymers andpoly(N-alkylaniline) can be inferred to be a result of

steric hindrance of the alkyl groups. The alkyl chains prevent the polymer chains from being

planar and shorten the conjugation lengths which are important for migrations of charge

carriers. The obvious solution is to synthesize an analogue of polymer 1 without a substituent

on N such as 19 (Scheme 15). Our attempts at synthesis of a non-substituted N-interrupted

conjugated polymer, .19 and its copolymer 20 from Pd-coupling polymerization of

corresponding monomers yielded only insoluble gels. It is possible that, during the

polymerization, a minor side reaction such as Pd-catalyzed arnination49 caused a slight

crossslinking. The resulting gel could not be separated from the ammonium salt formed

39

21 PdC^OPPr^ Cul Et3NorDBU Toluene

912^25

13. n 20. -■n

Scheme 15

during the polymerization. The insolubility and the presence of the salt in the polymers

prevented any meaningful property studies.

All the N-interrupted conjugated polymers are photoluminescent in both solution and

solid state. Excitation and emission spectra of THF solutions of polymers 1,2,3_,12,17 and

18 are shown in Figure 11. The emission spectra were acquired by using the Aex 20 nm lower

than the lower limits of the scanning ranges. The excitation spectra were recorded while the

emissions were monitored at 20 nm (Aem) higher than the upper limits of the scanning ranges.

The excitation spectra are similar to absorption spectra but the excitation bands are broader.

For polymers 12 and 18, only a single broad band was observed in the excitation spectra

(Figure 11) while three bands were observed in the absorption spectra (Figure 10). The

emissions of polymers 1,2, 4, .12 and ,18 tailed beyond 600 nm with peaks at 400-450 nm

corresponding to blue to green light. Polymer 17. however tails only to 500 nm with the

emission peak at 380-400 nm and the observed emission is blue. Emission spectra of polymer

40

1.4

1.2

1.0

S °*8 10 u c 3 u

0.6

0.4

0.2

0.0 300 350 4S0 500 SSO

Wavelength/nm s.o

K "i V-

4vwv\ f f^

600

m^2..

11— 300 350 450 6 0 0 6S0

Wavelength/nm Figure 11 Emission and Excitation spectra of polymers 1,2, 4, ,12,17 and 18 in THF

41

films of 1,4 and 12 on quartz substrates were also recorded (Figure 12). The spectra tail over

600 nm with the bands in the same range as the solution spectra. Even the peaks in film

spectra seem to be broader than the solution spectra, the film spectra showed more defined

electrovibronic coupling structures due to the fixed conformation in the solid state. Only the

film spectrum of polymer 4 is sufficiently resolved for an estimation of the vibration

frequency. The estimated vibrational frequency of ~ 2000 cm"1 corresponds to the stretching

of the triple bond (2200 cm"1).

The electroluminescent property of polymers 4 and 12 were studied by Dr. Shinar's

group using single layer light emitting diodes (LED) with ITO hole injector and Al electron

injector. The devices from polymer 3 emitted yellow green light while the devices from

a.of-

7.0f-

6.0!-i

si n

§ 4.01-O o

3.01-

2.0r

s' f \\ \ kf \ ' / if \i * \

1.0!- /

0.0- —

1..

A.

J j -'I v

X .

— I

250 300 350 400 450 500 550 Wavelength/nm

600 650 700 750

Figure 12 Emission spectra of polymer films of 1,4 and 12.

42

polymer 12 emitted blue light The efficiencies of these single layer devices were quite low

and the driving voltage was relatively high (> 20 V). These may due to an inefficient electron

injection and imbalanced charge transportation.

Ionization energy of electron donors can be estimated from a UV-Vis spectrum of

electron donor-acceptor (EDA) complex with I2 according to a linear relationship between

charge transfer energy (hvCT) and ionization energy (I15):50

hvCT = af + b

McConnell51 reported the coefficients a = 0.67 and b = -1.9 but Mulliken52 reported another

set of these coefficients where a = 0.87 and b = -3.6. The EDA complex of polymer 3 with I2

has a charge transfer band at 660 nm (1.87 eV) which gives ionization energy of 4.7 eV and

5.8 eV from McConnelTs coefficients and Mulliken's coefficients respectively. This

ionization energy well matches with the hole injector ITO workfunctions (3>rro ~ 4.8 eV).8

Electron affinity (EA) of the polymers can be calculated from the subtraction of ionization

energy with band edge energy. Polymer 3 has the band edge at 475 nm (2.6 eV) and the EA in

the range of 2.1 eV to 3.2 eV. This Ea is a little too low compared to the workfunction of Al

(<E>AI ~ 4.2 eV).8 It is also reasonable to assume that the holes travel through the polymer

films faster than the electrons because the polymers contain hole transporting moieties,

diphenylamine and carbazole, throughout the chain. However, this may not be conclusive as

UV-excited optically detected magnetic resonance (ODMR) studies, by Dr. Shinar's group, of

polymers 1, 4 and 12 suggesting structural defects of the polymer chains in the film state.53

The structural defect may reduce charge recombinations and stabilize triplet excitons resulting

in poor electroluminescent quantum efficiencies. Further investigation such as studies of

43

-,-5 Electrical conductivity of h doped PPE (c ~ 10° S cm"1)54 is about seven orders of

magnitude lower than that of I2 doped PPV (a ~ 102 S cm"1).55 It is thus interesting to see

whether this difference exists between N-interrupted polyphenylenevinylene, 24, and N-

interrupted PPE, 1. Polymer 24 was synthesized according to scheme 16.

?6H13

I-/ VN- r\ CuCN NC

DMF (78%)

TiCl4/Zn0

THF n (35%)

Mn = 2.45 x 104, Mw = 1.28 x 105

w Mn/Mw = 5.22, IV = 0.60 dL/g

r\

r\

^6H13

N—/ \—CN

1) LiAl(OEt)3H 2) H30+

y (56%)

96H13

26

O

Scheme 16

The key monomer, a dialdehyde 26, was obtained in 56% from a reduction of dicyano 25 with

triemoxyUtWumaluminiumhydride.56 The dicyano compound 25 was synthesized in 78% from

a double cyanylation of diiodo compound 6 (see Sheme 5 for the synthesis of this compound)

with CuCN.57 A reductive McMurry coupling polymerization58 of monomer 26 yielded the

desired polymer as a bright yellow solid in 35%. The polymer was first purified by

precipitation of methylene chloride solution of the polymer in methanol. The obtained

44

chloride solution by methanol. The obtained polymer has a distinct bimodal molecular weight

distribution. The lower molecular weight portion (< 10"4) can be largely removed by

precipitation of the polymer solution in acetone (Figure 13). The polymer obtained from

precipitation (twice in acetone) had Mn of 2.45 x 104 (DP = 87) with a broad polydispersity,

5.21. The intrinsic viscosity of this polymer was 0.60 dL/g. This polymer had poorer

solubility in organic solvents than its ethynylene analogue, polymer 1. A solution of polymer

24 in common organic solvents such as chloroform and THF became colloidal when the

concentration was over 10 mg/mL. The structural assignment of the polymer was achieved by

XH- and 13C-NMR. The XH-NMR spectrum (Figure 14) of 24 was fairly clean and fit well with

the expected structure with no significant signal of the polymer chain-ended, which implying

its high molecular weight

I B H X

X en o

c 3

5 . 0 0

4 . 0 0

3 . 0 0

2 . 0 0

1 . 0 0

0 0 7 . 0 0

Figure 13 Molecular weight distribution of polymer 24 obtained from a) a precipitation in

methanol and b) a precipitation in acetone.

45

Figure 14 ^-NMR spectrum of polymer 24 in CDC13.

Signals in the 13C-NMR spectrum of polymer 24 can be assigned by comparing the

spectrum to that of the corresponding dimer 27 (Figure 15). Dimer 27 was obtained in two .

steps from N-hexyldiphenylamine, 5 (Scheme 17). A Vilsmeier-Haack formylation of 5

yielded exclusively (95% yield) monoaldehyde 28 which was subjected to a reductive

McMurry coupling reaction to produce the desired dimer in 55%. The 13C-NMR spectra had

number of signals as expected, 11 and 15 for 24 and 27, respectively. The clean 13C-NMR

spectrum of 24 confirmed that the polymer was pure and its molecular weight was high. The

observation of exactly the same number of signals as expected for polymer 24 also strongly

suggested that the polymer chains contain only one geometrical isomer, presumably trans.

The six peaks observed between 10 to 55 ppm in both spectra corresponded to six carbons of

the hexyl side chain. The sp2-C signals were observed between 120-150 ppm with vinyl

carbon at 126 ppm.

46

CfiH 6n13

4N

a

-U-JJU**-~*J^ n

Pq

C6Hi3

m u

!A-!J_ii'4ih.

mtywmti.

— ■ — i1

" ! , — . . / i " ,■ • , 1 1 1 , 1 1 1 | : ! " " : ' — ; — " i "1 1

,1

" ' " — i " " | i n i | i i i i | i i M i i i — ; " > ' . " " , '

ISO 140 130 120 110 100 90 80 70 60 50 40

Figure 15 13C-NMR spectra of polymer 24 and dimer 27.

" I " " | " " i " ' ; " ■ ! 30 20 10 i

ppm

9eHi3

5

1) DMF, POCl3

Q 2 C 2 H 4 ?6H13

2)H20 (95%)

^Q_NHQ_i> m

TiCl4, Zn THF (55%) c „

I 6 13

22

Scheme 17

47

TGA showed a single weight loss at 392°C (95% rernaining weight) and only 9%

remaining weight at 1000°C. A UV-Vis absorption spectrum of polymer 24 in THF showed a

broad band with a X^* at 400 nm. Visibly, this polymer showed much stronger luminescence

than its ethynylene analogue, polymer 1. An emission spectrum of the THF solution showed

three emission peak at 457,488 and 515 nm. The energy differences between these three

peaks are 1390 and 1075 cm"1 which are considerably lower than the stretching energy of the

double bonds (1600-1650 cm"1) in the stilbene units. The differences in these energy remains

unexplained. Polymer 24 can form a homogeneous free standing film with bright yellow color

(Figure 8). This film is not as transparent as a film of polymer 1.

Electrical conductivities of polymer 24 measured by two in-line probes were lower

than the equipment threshold (< 10"9 S cm"1). Doping this polymer by iodine vapor was very

slow, but a conductivity of 1-10 S cm"1 was obtained after one day. The doping was

irreversible by vacuum but upon exposure to air the conductivity dropped below 10"9 S cm"1

within 5 minutes. The origin of this conductivity remains unclear but the slow oxidation of the

polymer by h to form tight radical ion pairs seems reasonable.

Ethynylene dendrimers containing triphenylamines

Dendrimers, sometimes called starburst dendrimers, refer to a class of well defined

oligomeric or polymeric compounds with highly branched structures.60 This new class of

compounds is composed of three distinct architectural features: an initiator core (T), interior

zones (II), and a surface region (TO.) (Figure 16). Repeating units in dendrimers possess three

or more linkages instead of two as in conventional linear polymers. In both the initiator core

48

and interior zones, the repeating units are attached to branching junctures. The propagating

repeating units of the interior zone will be capped with a terminal group to form the surface

region. Besides molecular weights (M„ and Mw), sizes of the dendrimers can be designated by

the number of interior zones called generations (n).

v%w'//,

* » » • * ,

©

•

Repeating Unit

Branching Juncture

Terminal Group

* • • " " " * * • ■ " " " " * n = Generation = Number of Interior Zones (II)

Figure 16 Architectural features of dendrimers.

Syntheses of dendrimers have become more intensive in the past decade, although the

concepts of dendritic structures61 and the first observation of dendritic structures in natural

proteins62 date back to 1943 and 1953, respectively. Due to their unique features, dendrimers

should possess special properties and offer diverse applications. Mechanical properties of the

dendrimers are usually inferior to those of the linear polymers. However, their employment as

composite additives in siloxane rubbers has lead to significant increases in their tensile

strengths. Better solubility of dendrimers in common solvents compared to linear polymers

containing similar repeating units were observed and rationalized.64 The solubilities in various

solvents can be altered by modification of the terminal groups at the surface.65 This surface

region can also provide a rich chemistry for the dendrimers. A pH-dependent aggregation of

49

acid-functionalized semi-dendrimers has been reported.66 Complexation of gold with dendritic

polyphosphines was reported to occur at the surface region with no marked difference in

reactivity when the generations of the dendrimers increase from 1 to 10.67 Electrochemical

studies of dendritic organosilicon containing peripheral ferrocenyl groups shows that all of the

ferrocenyl group can be oxidized at the same potential.68 Homogeneous catalysts based on

silane dendrimer-functionalized arylnickel (H) complexes are shown to be effective for

Kharasch addition.69 With precise sizes and shapes, these dendrimer-based catalysts offer

some advantages over conventional polymer-based catalysts, such as an all metal catalytic site

exposed to the reagents and substrate, an easy control of catalytic quality, and easy separation

and good recovery from the reaction mixture. While the surface region may provide several

varieties of interesting chemistry, the internal zones of the dendrimers have been the target of

research in guest-host chemistry.70 The internal zones contain many rigid or semi-rigid

cavities with precise sizes and shapes which can be utilized to selectively trap guest molecules

with proper sizes and shapes.

The choice of the repeating units and terminal groups can considerably alter the

properties of dendrimers as a whole. However, changing the generations of the dendrimers

can be used to fine tune these properties. This was observed, for example, in thermal

properties of the dendrimers, that lead to the design and synthesis of a novel class of liquid

crystalline macromolecules.71 Studies on the optical and electronic properties of dendrimers

began in 1994. UV-Vis absorption and emission of dendritic polysilanes and linear polysilane

have been compared.72 Moore modified his phenylacetylene-based dendrimers for a molecular

light funneling device.73 The molecule consists of peripheral diphenylacetylene chromophores

50

and longer conjugated phenylacetylene segments moving inward toward its center (Figure

17).The ends of each of these units are meta-linked to interrupt the conjugation between the

units. This design results in a smooth decrease in energy levels from the surface region to the

initiator core attached with a fluorescent probe, perylene.

position

Figure 17 Illustration duplicated from reference 73 showing structure and conceptual design

of the molecular light tunneling device.

51

Replacing the diphenylamine basic units in our linear N-interrupted polyphenylene-

ethynylene with triphenylamine would provide appropriate building blocks for the dendrimers

whose repeating units are closely related to those of the linear system. Comparing the

conductivity and photophysics of the dendrimers to those of the linear polymers should

confirm the effect of molecular shapes and dimensions on these properties. Thus, the

dendrimers containing 4,4\4"-tricarbynyltriphenylarrrine repeating units (Figure 18) were

synthesized.

Figure 18 General structure of dendritic 4,4\4"-carbynyltriphenylarriine.

Dendrimers can be obtained by two different approaches: single stage synthesis and

repetitive synthesis. Single stage synthesis involves polymerization of monomers containing at

least three polymerizable functional groups.63 Repetitive synthesis usually consists of

repetitive cycles of multisteps: protecting, coupling, and deprotecting. The former approach

is simpler and faster, but the resulting polymers are not structurally precise. Thus, it was

52

74

decided to utilize the second approach in our dendrimer syntheses.

Three major dendrimer growth schemes (Scheme 18), known as the "divergent",'

"convergent",75 and "double exponential growth",76 have been devised for repetitive synthesis.

For syntheses of dendrimers whose repeating units possess three branches, a key monomer,

BP3(2)n

After n cycles

T 3 ( 2 ) n ^ ^ A p T ^ n After n cycles

couple A+ B-*-AB

deprotect B-«-Bp

couple A+ B - ^ A B

deprotect A-*- Ap

Ap(Bp)22n

After n cycles

ApB, or B,

deprotect

AT2(2)n ' Convergent Growth

ABp2 B3(2)n Divergent Growth

Couple A+ B—»• AB

Ap(B)22n

A(Bp)22VAp Double Exponential Dendrimer Growth

Scheme 18

represented as AB2, generally contains two types of functional groups, A and B. The coupling

between these two functional groups should be virtually quantitative. Either A or B functional

groups needs to be protected and is represented by Ap or Bp. Therefore, two kinds of

monomers, ABp2 or ApB2, can be used. An ABp2 monomer is appropriate for the divergent

scheme while ApB2 is used for the convergent scheme. Both types of monomers are required

53

for the double exponential dendrimer growth. In the divergent scheme, three equivalents of

ABp2 react with an initiator core cpntaining three B functional groups, B3, producing Bp6.

After deprotection, the resulting B6can again couple with six equivalents of ABp2 monomer

generating a bigger dendrimer. The cycle can be repeated until the surface region becomes

too congested. For a rigid systems, however, this synthetic scheme is stopped rapidly, usually

after the first cycle, by the poor solubility of the products.43b The convergent scheme has been

used successfully for the synthesis of rigid dendrimers because the flexible terminal groups, T,

are introduced into the dendritic product from the first step.43 Li fact the number of these

flexible groups increases as the cycle is repeated. The products from the later cycles thus

generally possess greater solubilities.

The double exponential growth scheme allows the fastest dendritic growth per each

-cycle. However, it requires two types of monomers and two compatible protecting-

deprotecting reactions. The convergent scheme seems to best fit our system since we are

interested in the properties of the dendrimers. From the convergent scheme, three major

building blocks are required: a reactive initiator core (B3), a monomer (ApB2), and a reactive

terminal group (T3).

In the synthesis of our dendritic 4,4\4"-tricarbynyltriphenylamine, the reactive initiator

core is 4,4',4"-triiodotriphenylamine, TI3, the monomer is 4,4'-dtiodo-4"-trimethylsilyl-

ethynyltriphenylamine, SiETI2, and the reactive terminal groups are 4-ethynyl-N,N-

dialkylaniline, EAMe2 or EABu2 (Scheme 19)'. The synthesis of these building blocks used

the same reactions, with some modifications, as the synthesis of the monomers of the linear

polymers. The reactive initiator core, TI3, was obtained in 66% yield from the triple

54

3 eq. BTMAIC12

CaC03

CHCI3, MeOH reflux (66%)

I

Si =

E =

T =

Me3Si-

-csc-v-y

-tf^-ti v ^

IAMe2 R = Me (from Aldrich) IABu2R = Bu(91%)

k BTMAIC12

CaC03

CH2a2, MeOH

KOH/MeOH

O- -O NR2

HABu2R = Bu

NR,

EAMe2R = Me(95%) EABu2 R = Bu (93% for two step:

reactive terminal groups

Scheme 19

55

iodination of triphenylamine, TH3, by three equivalents of BTMAIC12 under reflux

temperature of CHC13 for 72 h. An attempt to shorten the reaction time by use of a stronger

iodinating agent ICl, did not yield the desired product It is worth mentioning that the direct

Pd-coupling of one equivalent of trimethylsilylacetylene with TI3 is a statistical reaction.

However, the desired monomer SiETI2 was obtained in satisfactory yield (43% isolated)

along with 18% recovery of starting material TI3,17% of 4-iodo-4',4"-bistrimethyl-

silylethynylniphenylamine, (SiE)2TI, and 2 % of 4,4\4"-tristrimethylsilylethynyltriphenyl-

amine, T(ESi)3.The isolation of the monomer was achieved by repetitive flash

chromatography. The synthesis of the reactive terminal groups was straightforward and the

desired compounds were obtained in excellent yields.

The synthesis of the zero generation (GO) dendrimer was accomplished by a Pd-

coupling of TI3 with three equivalents of EAMe2 (Scheme 20). For higher generations, the

EABu2 was utilized as the reactive terminal group to ensure solubilities of the products. A

Pd-coupling of two equivalents of EABu2 with monomer SiETI2 yielded the protected

NMe.

3eq. EAMe2

PdCl2(PPh3)2

Cul, DBU Toluene (83%) ff^T

M e , ^ ' ^

Scheme 20

NMe„

56

monodendron SiET(EABu2)2 in 77% yield. The monodendron ET(EABu2)2 was obtained

from base-catalyzed desilylation of SiET(EABu2)2 in 98% yield. A Pd-coupling of three

equivalents of this monodendron with TI3 gave the desired Gl in 93% yield (Scheme 21).

The synthesis of G2 involved repeating coupling-deprotecting sequences. The monomer

SiETI2 was coupled with two equivalents of ET(EABu2)2 to form SiET[ET(EABu2)2]2

(Scheme 22). The desilylation of SiET[ET(EABu2)2]2 yielded ET[ET(EABu2)2]2, another

monodendron, which can be coupled with one third equivalent of TI3 to give the desired G2.

Me3Si—=

2 eq. EABu2

PdCl2(PPh3)2

Cul, DBU Toluene

l (83%)

*► M e 3 S i - = E - ^ - ]

SiET(EABu2)2\=

KOH MeOH, THF (98%) NBu,

1/3 eq. TI3 PdCl2(PPh3)2

Cul, DBU <' Toluene (93%)

NBu,

Gl

Scheme 21

57

SiMe,

SiETI

Bu2N.

2 eq. ET(EABu2)2

PdQ2(PPh3)2

Cul, DBU Toluene (70%)

MeOH, THF jf (98%)

1/3 eq. TI3

PdCl2(PPh3)2

Cul, DBU Toluene mu2 (73%)

P

NBu,

NBu,

G2

Scheme 22

58

Structural assignments of Gl and G2 were accomplished by 13C-NMR. The spectra of

Gl and G2 showed four and six characteristic peaks, respectively. The peaks at 146-148 ppm

corresponded to sp2-C's attached to N and the peaks at 86-91 ppm corresponded to the

acetylene carbons (Figure 19). Molecular weights of the dendrimers were determined by GPC

- N / ^ |4« |4I 141 fit |«4 |«|

I—

G2

i- ~iUU «A

t l M.3 M M.J H M-S M tl.i it

ll 120 I tS 100 81

ppm Figure 19 13C-NMR spectra of Gl and G2 and their characteristic peaks assignments

59

NBu,

Bu2N.

NBu,

Figure 19 (continued)

60

Table 5 Formulas, formula weights (F.W.), and observed molecular weights from GPC (Mn

Mw) and MS (M-*) of synthesized dendrimers.

Dendrimer Formula F.W. observed molecular weight

Mn Mw M+

GO

Gl

G2

GttH-uNt 674.34

C174H180Nio 2,411.45

C39oH384N22 5,379.49

NA

2,400

5,210

NA

2,470

5,250

674.3414

2,411.47

5,374.2

and MS (Table 5). For GO, an exact mass of 674.3414 (calc. 674.3410) was obtained from

high resolution EI. The molecular weight of Gl obtained from low resolution EI was

comparable to the formula weight. A matrix assisted laser desorption/ ionization (MALDI)

technique was required to obtain the molecular ion mass of G2. An acceptable mass (5374.2)

was obtained when a-cyano-4-hydroxycinamic acid was used as a matrix and Gl was used as

a reference. The GPC gave satisfactory Mn with very narrow polydispersities (1.02 and 1.01

for Gl and G2, respectively) indicating the precise sizes of these dendrimers. Geometry

optimizations of GO, Gl and G2 were performed on HyperChem™ using MM+ molecular

mechanics calculation. For Gl and G2, the butyl groups were replaced by methyl groups for

simplicity of the calculation. The resulting three dimensional structures of these three

dendritic molecules displayed that the molecular structure of GO and Gl were almost two

dimensional whereas G2 developed an extensive three dimensional structure (Figure 20). The

radii from the N of the initiator core to the peripheral N of GO, Gl, and G2 were 12.1 A, 21.1

A and 28.6 A, respectively.

61

Figure 20 Three dimensional structures of GO, Gl and G2.

62

The UV-Vis absorption spectra showed that GO had a Xm^ at 378 nm, and both Gl

and G2 had the same X^* at 386 nm. The same X^ of Gl and G2 suggests no extensive

conjugation beyond the dimer of 4-carbynyltriphenylamine. The 8 nm difference in the X^ is

likely due to the difference in their basic chromophores, not the extension of the conjugation.

Gl and G2 contain a chromophore, bis(4,4'-triphenylamine) acetylene, which was not present

in GO. The absorption maxima of Gl and G2 were close to the Xmax (389 nm) of the linear

polymer 1 suggesting the similarity of electronic properties of these two types of polymers.

Gl and G2 were photoluminescent and excitation and emission spectra of their THF

solutions were recorded (Figure 21). The emission spectra contained three partially resolved

peaks spreading from 375 to 575 nm, similar to those observed in polymer 1. The

photoluminescence of the dendrimers appeared much stronger than that of polymer 1. This

result was opposite to what was observed in the silane system.72 G2 also showed

electroluminescence, but the stabilities and quantum efficiencies of the devices based on this

dendrimer have not been satisfactory yet

The electrical conductivity of G2 was similar to that of polymer 1. The conductivity

increased from < 10"9 to -lO6 when the dendrimer was doped with iodine vapor. This result

indicated no effect of shapes, dimensions, or conformations on the conductivity of this

polymer system. Therefore, it was reasonable to assume that electron hopping, rather than the

electron migration through the jc-conjugated bonds, was responsible for conductivity in these

polymers. The previously described spectroscopic data also indicated that the electronic

properties of these polymers depended mostly on individual repeating units.

63

1.00-

0.90

0.80

0.70

r* 0.60 n c 3 0.50 o u

0.30

0.20

0.10

V

v ^r\ \ \ \

\ ky~'

I "v

-vv^i

300

300 350

400 450 500

Wavelength/nm 550

450

Wavelength/nm 500 550

Figure 21 Excitation and emission spectra of Gl and G2.

64

Thermal behavior of these dendrimers was studied by DSC scanning from room

temperature to 400°C for GO and to 350°C for Gl and G2, with a 20°C/min ramp. The DSC

thermogram of GO showed a melting point at 278°C and an interesting endothermic and

exothermic peaks at 145 and 157° C (Figure 22). These endo/exothermic peaks werenot

observed when the compound previously heated (to 200°C) was reheated, indicating an

irreversible phase transition. However, these peaks could be restored by recrystallization of

the compound in methanol/methylene chloride. The TGA thermogram of GO showed no

weight loss below 350°C, excluding a loss of solvent from a solvent-inclusion crystal. X-ray

powder diffraction of the preheated material and postheated material showed different

patterns of sharp diffractions, indicating two types of crystals. Therefore, these

endo/exothermic peaks were likely due to melting-crytallization transition.77 Conformational

changes maybe involved in this transition, which should be obvious in X-ray crystallogaphy.

Unfortunately, a high quality single crystal could not be obtained. The DSC thermograms of

Gl and G2 consisting of small endothermic peaks cannot be unambiguously interpreted.

An attempt to synthesize G3 was also conducted. The repetitive convergent scheme

was again utilized (Scheme 23). The coupling of three equivalents (with 20 % excess) of

monodendron ET[ET[ET(EABu2)2]2]2 with TI3 in the final step yielded an inseparable

mixture, possibly the didendron and G3. The ^-NMR spectrum showed the presence of an

iodophenyl group. The GPC chromatogram showed two greatly overlapping peaks with Mn =

1.48 x 104 and Mw = 1.61 x 104 (Figure 23). Presumably, steric hindrance of the branches

surrounding the reactive focal point reduces the reactivity of the didendron toward the third

coupling.43b

65

-z-> j i

-3-i ISO EDO 250

"eaoeraru-e !*C1 300 330 400

Sent-»1 V4.CD O-jPont =05

300 330 400 General V4.03 SuPont EOC:

0.2-

0.0-

5 I -°-2" 5

-0 .4-

-0 .6-

- 0 . 8 -

G2

\- _

^ ^ \ 7 9 . « * :

50 100 150 ZOO 250 300 350 Temperature (*CI General V4.00 OuPont 20CC

Figure 21 DSC thermograms of GO, Gl and G2.

66

SiMe,

SiETI 2 eq. ET[ET(EABu2)2]2

PdCl2(PPh3)2

Cul, DBU T o l u e n e SMe (81%) b l M e 3 Bu2N

Bu.

NBu,

NBu, SiET[ET[ET(EABu2)2]2]

NBu2 Bu2N-

Bu2N

|KOH/MeOH,THF f(99%)

NBu,

NBu,

ET[ET[ET(EABu2)2]2]2

NBu2 Bu2N-

PdCl2(PPh3)2

Cul, DBU Toluene

G3

Scheme 23

67

3.80

. BBE

DUAL CHROHATOGKAH

0 + B X

z w z

w

2.88 -

1.88 -

"n« X.48E4 Hw= X.BXE4

~ Mz« X.88E4 UISC CHROMATOGRAM CONC CHROMATOGRAM

^ 7 . e ' 3 3 . 0 3 a . 0 ' <*tf

RET UOL CnL)

Figure 23 GPC chromatograms of the product from a Pd-coupling of two equivalents of

ET[ET[ET(EABu2)2]2]2 with TI3.

68

EXPERIMENTAL

Characterizations of all synthesized compounds were based on exact mass, IR,

UV/Vis, ^-NMR and 13C-NMR.. The exact masses were obtained from a Kratos MS 50

mass spectrometer with 10,000 resolution. The infrared spectra were recorded on a Bio-Rad

Digilab FTS-7 spectrometer from neat samples. The UV/Vis spectra were acquired on a

Hewlett Packard 8452A diode array UV/Vis spectrometer and X^a. were determined at optical

densities of 0.2-0.5. The XH and 13C NMR spectra were collected on a Varian VXR-300 MHz

spectrometer in deuterated chloroform solution unless otherwise specified. Tentative signal

assignments of 13C-NMR spectra are given in parentheses after each chemical shift. Reactions

were monitors by Hewlett Packard 5890 series n GC and Hwelett Packard tandem GC-IR-

MS (5890A GC-5965AIR-5970 Series MS).

The thermal responses of polymers were studied on Du Pont Instruments 951

Thermogravimetric Analyzer (TGA) and 910 Differential Scanning Calorimeter (DSC) with a

scanning rate of 20°C/min for both analyses. Molecular weight distribution of polymers were

detemined by gel permeation chromatograph (GPC) system using universal calibration against

polystyrene standards (Mn = 2,000 -170,000). The GPC system consisted of a Beckman

HOB solvent delivery system, a Perkin-Elmer 601 liquid chromatograph equipped with six

Beckman 10 \i U-spherogel (7.7 mm x 30 cm) columns, a Viscotek 110 differential

viscometer and a Waters Associates R401 differential refractometer. The viscometer and

refractometer were parallel connected. The GPC analysis was performed at a flow rate of 1.0

mL/irdn of THF.

69

THF was distilled over Na-benzophenone and ether was distilled over CaH2

immediately before use. Commercially available reagents were used as receivedd unless

otherwise specified. Scientific Adsorbents 40 u. silica gel was utilized in flash

chromatography.

N-Hexyldiphenylamine, 5

A 500 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with diphenylamine (8.46 g, 50 mmol), pulverized 87% KOH (19.35 g, 300 mmol),

K2CC<3 (10.37 g, 75 mmol) and tetrabutylammoniumbromide (1.61 g, 5 mmol) and toluene

(100 mL). Bromohexane (9.25 g, 56 mmol) was added slowly to this stirred mixture. After

24 h, of reflux the mixture was filtered and the filtrate was washed with 1M HCl (2 x 100

mL). The solvent was removed and the remaining yellow oil was eluted through a flash silica

gel column by hexane. The product was collected and the solvent was removed to give the

desired product (10.53 g, 82 %) as a colorless Uquid. BR (cm"1) 1497,2937,3073; *H-NMR:

8 0.90 (3 H, t/7.0), 1.32 (6 H, m), 1.68 (2 H, qui/ 8.0), 3.70 (2 H, t / 8.0), 6.95 (2 H, tJ

9.0), 7.01 (4 H, d/9.0), 7.27 (4 H, t/9.0); 13C-NMR: 8 14.0 (CH3), 22.6 (CH2), 26.7

(CH2), 27.4 (CH2), 31.6 (CH2), 52.3 (CH2), 120.8 (4 sp2-CH), 121.0 (2 sp2-CH), 129.2 (4

sp2-CH), 148.1 (2 sp2-C).

4,4'-diiodo-N-hexyIdiphenylamine,6

A 1000 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar,

was charged with N-hexyldiphenylamine (10.21 g, 40 mmol) in methylene chloride (300 mL)

70

and methanol (100 mL). Benzyltrimethylammonium chloroiodate,47 BTMAIC12, (30.64 g, 88

mmol) and CaC03 (11 g, 0.11 mol) was added quickly to this stirred solution. After 20 h,

20% NaHS03 solution was added to this mixture until the mixture became colorless. The

organic layer was separated and the aqueous layer was extracted with methylene chloride (2 x

50 mL). The combined organic layer was washed with water (2 x 100 mL) and dried over

anhydrous MgSQ*. The mixture was concentrated and the residue was eluted through a flash

silica gel column by hexane. The solvents was removed the resulting yellow oil was dried

under vacuum at 65 °C for 24 h. to give the desired product (4.40 g, 86%). HIRES EI: calcd

for Ci8H21NI2 504.9763, measured 504.9694; IR (cm-1): 1484,1557,1589,2924,2952, 3028,

3060; -NMR: 8 0.86 (3 H, t/7.0), 1.26 (6 H, m), 1.54 (2 H, qui J 7.0), 3.60 (2 H, tJ

7.0), 6.73 (4 H, d/9.0), 7.51 (4 H, d/9.0); 13C-NMR: 8 14.0 (CH3), 22.6 (CH2), 26.6

(CH2), 27.1 (CH2), 31.5 (CH2), 52.2 (CH2), 83.9 (2 sp2-C), 129.0 (4 sp2-CH), 138.1 (4 sp2-

CH), 147.1 (2 sp2-C).

4,4'-bistrimethyIsiIylethynyI-N-hexyldiphenylamine,7

A 1000 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar,

was charged with 4,4'-dnodo-N-hexylchphenylamine (6.00 g, 11.9 mmol), PdCl2(PPh3)2 (82

mg, 0.12 mmol) and Cul (22 mg, 0.12 mmol) in triethylamine (25 mL) and toluene (20 mL).

Trimethylsilylacetylene (2.56 g, 26.1 mmol) was added dropwise to this stirred solution. After

12 h, the mixture was filtered and the filtrate was washed with 1 M HCl (2 x 30 mL). The

solvent was removed and the residue was eluted through a flash silica gel column by hexane.

The product was collected and the solvent was removed. The product was dried under

71

vacuum for 24 h to give the desired product (5.29 g, 100%) as a yellow oil. HIRES EI:

calcd for C^HgoNSiz 445.2621, measured 445.2633; IR (an1): 1498,1594,2188,2856,

2927,2953,3038; *H-NMR: 8 0.22 (18 H, s), 0.85 (3 H, t/7.0), 1.25 (6 H, m), 1.59 (2 H,

qui / 7.0), 3.65 (2 H, t / 7.0), 6.87 (4 H, d / 9.0), 7.33 (4 H, d / 9.0); 13C-NMR: 8 0.1 (3

CH3), 14.0 (CH3), 22.6 (CH2), 26.6 (CH2), 27.3 (CH2), 31.5 (CH2), 52.1 (CH2), 93.0 (2 sp-

C), 105.4 (2 sp-C), 115.5 (2 sp2-C), 120.4 (4 sp2-CH), 133.1 (4 sp2-CH), 147.4 (2 sp2-C).

4,4'-diethynyl-N-hexyIdiphenylamine,8

A 1000 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar,

was charged with 4,4'-bistrimethylsUylemynyl-N-hexyldiphenylamine (4.62 g, 10.4 mmol) in

methanol/isopropanol (50 mL/50mL). Saturated KOH aqeous solution (0.2 mL) was added

dropwise to this stirred solution. After 30 min the mixture was neutralized by IM HCl before

water (50 mL) and hexane (50 mL) were added. The organic layer was separated and the

aqeous layer was extracted with hexane (2 x 30 mL). The combined organic layer was dried

over anhydrous MgS04 and the solvent was removed. The residue was eluted through a flash

silica gel column by hexane. The solvent was removed and the product was dried under

vacuum for 24 h to give the desired product (2.84 g 91%) as a yellow oil. HIRES EI: calcd

for C22H23N 301.1839, measured 301.1839; UV (CHCI3, nm): 339,279; IR (GC-IR): 1504,

2106,2938,3331; XH-NMR: 8 0.87 (3 H, t J7.0), 1.28 (6 H, m), 1.63 (2 H, qui/7.5), 3.02

(H, s), 3.68 (2 H, t J7.5), 6.93 (4 H, d / 9.0), 7.38 (4 H, d / 9.0); 13C-NMR: 8 14.0 (CH3),

22.6 (CH2), 26.6 (CH2), 27.3 (CH2), 31.5 (CH2), 52.1 (CH2), 76.2 (2 sp-CH), 83.8 (2 sp-C),

114.5 (2 sp2-C), 120.5 (4 sp2-CH), 133.2 (4 sp2-CH), 147.6 (2 sp2-C).

72

PoIy-4,4'-ethynyIene-N-hexyldiphenylamine (Polymer 1)

A100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 4,4'-diethynyl-N-hexyldiphenylamine (0.30 g, 1 mmol), 4,4'-diiodo-N-

hexyldiphenylamine (0.50 g, 1 mmol), DBU (1 mL), toluene (20 mL) and rriemylamine (20

mL). PdCl2(PPh3)2 (14 mg, 0.02 mmol) and Cul (14 mg, 0.07 mmol) were added quickly to

this stirred solution, After 16 h, the mixture was warmed to 50°C and the stirring was

continued for 6 h. The mixture was allowed to cool to ambient temperature and was then

filtered. The solid was washed several times with warm toluene and the combined filtrate was

concentrated to 40 mL and was then dropped into methanol (200 mL). The yellow precipitate

was collected and reprecipitated in methanol from toluene solution. The yellow precipitate

was dried under vacuum at 65°C for 24 h to give the desired polymer (0.52 g, 94%). UV

(THF, nm): X^ = 389; IR (an1): 1510,1598,2210,2856,2926,2953, 3038; ^-NMR: 8

0.87 (3 H, br.), 1.29 (6 H, br.), 1.64 (2 H, br.), 3.70 (2 H, br.), 6.96 (4 H, d / 8.5), 7.39 (4 H,

d/8.5); 13C-NMR: 814.0 (CH3), 22.6 (CH2), 26.7 (CH2), 27.4 (CH2), 31.6 (CH2), 52.2

(CH2), 88.8 (2 sp-C), 116.0 (2 sp2-C) 120.5 (4 sp2-CH), 132.4 (4 sp2-CH), 147.0 (2 sp2-C);

GPC: Mn = 3.09 x 104, Mw = 5.24 x 104, M*/Mn = 1.70, IV = 0.63 dl/g.

Polymer 2

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 4,4'-diemynyl-N-hexyldiphenylamine (0.30 g, 1 mmol), 1,4-diiodobenzene (0.33

g, 1 mmol), PdCl2(PPh3)2 (14 mg, 0.020 mmol), Cul (10 mg, 0.052 mmol) and toluene (15

mL). DBU (0.8 mL) was added dropwise to this stirred solution. After 20 min., 40 min and

73

60 min additional toluene (5 mL) was added to the mixture to prevent a precipitation of the

forming polymer. After 6 h, the mixture was filtered. The precipitate was washed several

times with warm toluene and the combined filtrate was concentrated to 40 mL and then

dropped into methanol (200 mL). The yellow precipitate was collected and reprecipitated in

methanol from THF (40 mL) solution. The precipitate was dried under vacuum at 65°C for

24 h to give 2 (0.36 g, 97%). UV (THF, nm): X^ = 400; IR (cm"1): 1498,1594,2210,

2856,2927,2954,3038; XH-NMR: 8 0.86 (3 H, br.), 1.29 (6 H, br.), 1.64 (2 H, br.), 3.73 (2

H, br.), 4.01 (4 H, br.), 6.98 (4 H, d / 8.0), 7.42 (4 H, d J 8.0), 7.46 (4 H, s); 13C-NMR: 8

14.0 (CH3), 22.6 (CH2), 26.7 (CH2), 27.4 (CH2), 31.6 (CH2), 52.2 (CH2), 88.5 (2 sp-C), 91.5

(2 sp-C), 115.5 (2 sp2-C), 120.7 (4 sp2-CH), 123.0 (2 sp2-C), 131.3 (4 sp2-CH), 132.8 (4 sp2-

CH), 147.4 (2 sp2-C); GPC: Mn = 1.03 x 104, Mw = 3.16 x 104, MJM„ = 3.07, IV = 0.96

dl/g.

Polymer 3

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 4,4'-diethynyl-N-hexyldiphenylamine (0.30 g, 1 mmol), 1,4-diiodobenzene (0.53

g, 1 mmol), PdCl2(PPh3)2 (10 mg, 0.014 mmol), Cul (5 mg, 0.026 mmol) and toluene (10

mL). DBU (0.9 mL) was added dropwise to this stirred solution. After 30 min toluene (15

mL) was added to the mixture. After 16 h, the mixture was filtered. The solid was washed

several times with warm toluene and the combined filtrate was concentrated to 40 mL by

rotating evaporation. The concentrated filtrate was dropped into methanol (200 mL). The

yellow precipitate was collected and reprecipitated in methanol from THF (40 mL) solution.

74

The precipitate was dried under vacuum at 65°C for 24 h to give 4 (0.54 g, 93%).UV (THF,

nm): X^ = 416; -NMR: 8 0.88 (9 H, br.), 1.29-1.34 (14 H, m.), 1.54 (4 H, br.), 1.65 (2

H, br.), 1.83 (4H, qui/7.0), 3.71 (2 H, br.), 4.01 (4 H, t/7.0.), 6.96 (4 H, d/8.0), 6.98 (2

H, s), 7.42 (4 H, d/8.0); 13C-NMR: 814.1 (3 CH3), 22.6 (3 CH2), 25.7 (2 CH2), 26.7

(CH2), 27.4 (CH2), 29.3 (2 CH2), 31.6 (3 CH2), 52.2 (CH2), 69.6 (2 CH2), 85.3 (2 sp-C), 95.1

(2 sp-C), 114.0 (2 sp2-C), 116.0 (2 sp2-Q, 116.8 (2 sp2-CH), 120.5 (4 sp2-CH), 132.7 (4 sp2-

CH), 147.3 (2 sp2-C), 153.5 (2 sp2-C); GPC: Mn = 1.68 x 104, Mw = 2.68 x 104, M*/Mn =

1.60, IV = 0.62 dl/g.

Polymer 4

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 4,4'-diethynyl-N-hexyldiphenylamine (0.51 g, 1.7 mmol), 2,5-diiodo-l,4-

dioctoxybenzene (0.99 g, 1.7 mmol), DBU (1 mL), toluene (40 mL) and triethylamine (20

mL). PdCl2(PPh3)2 (26 mg, 0.037 mmol) and Cul (26 mg, 0.14 mmol) were added quickly to

this stirred solution. After 16 h, the mixture was warmed to 50°C and the stirring was

continued for 6 more hour. The mixture was allowed to cool to ambient temperature and was

then filtered. The solid was washed several times with warm toluene and the combined filtrate

was concentrated to 50 mL and was then dropped into methanol (250 mL). The yellow

precipitate was collected and reprecipitated in methanol from a toluene solution. The

precipitate was dried under vacuum at 65°C for 24 h to give 4 (0.95 g, 89%). UV (THF,

nm): X^ =414; IR (an1): 1512,1594,2142,2203,2855,2925,2952, 3037; -NMR: 8

0.85 (9 H, br.), 1.27 (22 H, br.), 1.54 (4 H, br.), 1.64 (2 H, br.), 1.83 (4 H, br), 3.70 (2 H,

75

br.), 4.01 (4 H br.), 6.98 (6 H, br.), 7.40 (4 H, br); 13C-NMR: 814.0 (CH3), 14.1 (2 CH3),

22.6 (CH2), 22.7 (2 CH2), 26.1 (2 CH2), 26.6 (CH2), 27.4 (CH2), 29.3 (2 CH2), 29.4 (4 CH2),

31.6 (CH2), 31.8 (2 CH2), 52.3 (CH2), 69.6 (2 CH2), 85.3 (2 sp-C), 95.1 (2 sp-C), 114.0 (2

sp2-C), 116.0 (2 sp2-C), 116.8 (2 sp2-CH), 120.5 (4 sp2-CH), 133.8 (4 sp2-CH), 147.3 (2 sp2-

C), 153.5 (2 sp2-C); GPC: M„ = 2.58 x 104, Mw = 6.27 x 104, MJM n = 2.43, TV = 0.38 dl/g.

Poly-4,4'-butadiynyIene-N-hexyIdiphenylamine (polymer 12)

A 25 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with CuCl (0.50g, 5.1 mmol) and 9 mL THF. Tettamethylethylenediamine, TMEDA,

(0.25 mL, 1.7 mmol) was added to this stirred solution. After 45 min the solution was

allowed to settle, leaving a clear deep blue-green solution of the CuCl-TMEDA complex.

Another 100 mL flask, equipped with a magnetic stirring bar, thermometer, cold-finger

condenser and 0 2 inlet-outlet tubes, containing THF (10 mL) and 4-ethynyl-N,N-

dimethylanilne (1.16 g, 38 mmol) was charged with a rapid stream of 02. The solution of

CuCl-TMEDA complex (2 mL) freshly prepared as described above was added dropwise to

this stirred solution. The temperature was maintained at 35°-45°. THF (10 mL) was added

again after 30 min and 1 h to prevent a precipitation of the polymer. After 5 h, the solution

was filtered and the solid was washed several times with THF. The filtrate was combined and

concentrated to 50 mL before dropping into methanol (200 mL). The yellow polymer was

collected and reprecipitated in methnol from THF solution. The polymer precipitate was dried

under vacuum at 65°C for 24 h to yield 12 (0.99 g, 87%). UV (THF, nm): X^ = 399; IR

(cm'1): 1590,1605,2143,2207,2858,2928,2956,3038; XH-NMR: 8 0.85 (3 H, br.), 1.27

76

(6 H, br.), 1.59 (2 H, br.), 3.69 (2 H br.), 6.93 (4 H, d / 8.0), 7.39 (4 H, d / 8.0); 13C-NMR:

814.0 (CH3), 22.6 (CH2), 26.6 (CH2), 27.4 (CH2), 31.5 (CH2), 52.3 (CH2), 73.6 (2 sp-C),

81.9 (2 sp-C), 114.4 (2 sp2-Q 120.6 (4 sp2-CH), 133.7 (4 sp2-CH), 147.0 (2 sp2-C); GPC:

Mn = 4.99 x 104, Mw = 7.00 x 104, MJMn = 1.40, IV = 0.78 dl/g.

N-octylcarbazole, 13

A 500 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with carbazole (16.7 g, 0.100 mol), pulverized 87% KOH (38.7 g, 0.600 mol),

K2C03 (20.7 g, 0.150 mol), tetrabutylammonium bromide (3.22 g, 10 mmol) and toluene (200

mL). 1-Bromooctane (19.3 g, 0.100 mol) was added slowly to this stirred solution. After 16

h of reflux, the mixture was allowed to cool to room temperature and was filtered. The

filtrate was washed with IM HCl (2 x 100 mL) and dried over anhydrous MgSC«4. The

solvent was removed and the remaining yellow oil was eluted through flash silica gel columns

by hexane. The product was collected and the solvent was removed to give 13 (28.3 g, 98 %)

as a light yellow liquid. XH-NMR: 8 1.18 (3 H, t/7.0), 1.49-1.57 (10 H, m), 2.04 (2 H, qui /

7.0), 4.40 (2 H, t/7.0), 7.50 (2 H, tJ 8.0), 7.60 (2 H, d / 8.0), 7.72 (2 H, t / 8.0), 8.37 (2 H,

d / 8.0); 13C-NMR: 8 14.3 (CH3), 22.7 (CH2), 27.2 (CH2), 28.9 (CH2), 29.4 (CH2), 29.5

(CH2), 31.9 (CH2), 42.4 (CH2), 108.4 (2 sp2-CH), 118.3 (2 sp2-CH), 120.1 (2 sp2-CH), 122.1

(2 sp2-C), 125.3 (2 sp2-CH), 139.8 (2 sp2-C).

77

3,6-diiodo-N-octylcarbazole, 14

A 500 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with N-octylcarbazole (6.40 g, 23 mmol), CaC03 (11 g, 0.11 mol), methylene

chloride (150 mL) and methanol (50 mL). A solution of iodinemonochloride (ICl) in

methylene chloride (IM, 46 mL, 46 mmol) was added dropwise to this stirred solution. After

8 h, another portion of 1 M ICl (10 mL, 10 mmole) was added. After additional 8 h of

stirring, the mixture was added with 20% NaHS03 solution until the mixture became pale

yellow. The organic layer was separated and the aqueous layer was extracted with methylene

chloride (2 x 50 mL). The combined organic layer was washed with water (2 x 100 mL) and

dried over anhydrous MgSC>4. The solvents were removed and the resulting solid was

crystallized from acetone and dried under vacuum at 65 °C for 24 h to give 14 (10.9 g, 90%)

as a white solid. m.p.: 96°C; HIRES EI: calcd for C20H24NI2 (M+H) 531.9998, measured

531.9792; BR (cm-1): 1497,2852,2924,2952; XH-NMR: 8 0.85 (3 H, t/7.0), 1.21-1.28 (10

H, m), 1.78 (2 H, qui/7.0), 4.15 (2 H, t/7.0), 7.12 (2 H, d/8.5), 8.27 (2 H, dd / 8.5,1.5),

8.28 (2 H, d/1.5); 13C-NMR: 8 14.0 (CH3), 22.6 (CH2), 27.2 (CH2), 28.8 (CH2), 29.1

(CH2), 29.3 (CH2), 31.7 (CH2), 43.2 (CH2), 81.6 (2 sp2-C), 110.8 (2 sp2-CH), 123.9 (2 sp2-

C), 129.3 (2 sp2-CH), 134.4 (2 sp2-CH), 139.4 (2 sp2-C).

3,6-bistrimethylsilylethynyl-N-octyIcarbazole, 15

A 250 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 3,6-diiodo-N-octylcarbazole (5.31 g, 10.0 mmol), PdCl2(PPh3)2 (56 mg, 0.080

mmol), Cul (38 mg, 0.20 mmol), triethylamine (35 mL) and toluene (35 mL).

78

Trimethylsilylacetylene (2.06 g, 21 mmol) was added dropwise to this stirred solution. After

12 h, the mixture was filtered and the filtrate was washed with 1M HCl (2 x 30 mL). The

solvent was removed and the residue was eluted through a flash silica gel column by hexane.

The product was collected and the solvent was removed. The product was dried under

vacuum for 24 h to give the desired product (3.86 g, 82%) as a white solid. ^-NMR: 8 0.31

(9 H, s), 0.87 (3 H, t/7.0), 1.23-1.30 (10 H, m), 1.81 (2H, qui/7.0), 4.21 (2 H, t/7.0),

7.27 (2 H, d/8.5), 7.57 (2 H, dd/8.5,1.5), 8.20 (2 H, d/1.5); 13C-NMR: 8 0.16 (3 CH3),

14.0 (CH3), 22.6 (CH2), 27.2 (CH2), 28.9 (CH2), 29.1 (CH2), 29.3 (CH2), 31.7 (CH2), 43.2

(CH2), 92.0 (sp-C), 106.4 (sp-C), 108.7 (2 sp2-CH), 113.7 (2 sp2-C), 122.3 (2 sp2-C), 124.6

(2 sp2-CH), 129.9 (2 sp2-CH), 140.5 (2 sp2-C)

3,6-diethynyl-N-octyIcarbazole, 16

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 3,6-bistrimethylsilylethynyl-N-octylcarbazole (1.43 g, 3 mmol) in methanol/

isopropanol (20 mL/20mL). Saturated KOH aqueous solution (0.1 mL) was added dropwise

to this stirred solution. After 30 min the mixture was neutralized by IM HCl before water (20

mL), toluene (10 mL) and hexane (20 mL) were added. The organic layer was separated and

the aqeous layer was extracted with hexane (2 x 30 mL). The combined organic layer was

dried over anhydrous MgSC^ and the solvent was removed. The residue was eluted through a

flash silica gel column by hexane. The solvent was removed and the product was dried under

vacuum for 24 h to give 16 (0.73 g 70%) as a yellow solid, mp: 65°C, HIRES EI: calcd for

QMHZSN 327.1983, measured 327.1987, IR (cm"1): 1598,1630,2104, 2854,2926,2954,

79

3306, -NMR: 8 0.86 (3 H, t/7.0), 1.24-1.29 (10 H, m), 1.78 (2 H, qui/7.0), 3.09 (H, s),

4.16 (2H, t/7.0),7.26 (2H, d/8.5), 7.57 (2H, dd/8.5,1.5), 8.18 (2H, d/1.5); 13C-

NMR: 8 14.0 (CH3), 22.5 (CH2), 27.1 (CH2), 28.8 (CH2), 29.1 (CH2), 29.2 (CH2), 31.7

(CH2), 43.2 (CH2), 75.4 (sp-CH), 84.7 (sp-C), 108.8 (2 sp2-CH), 112.6 (2 sp2-C), 122.1 (2

sp2-C), 124.6 (2 sp2-CH), 130.0 (2 sp2-CH), 140.5 (2 sp2-C)

Polymer 17

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 3,6-diethynyl-N-octylcarbazole (0.33 g, 1 mmol), 3,6-diiodo-N-octylcarbazole

(0.53 g, 1 mmol), PdCl2(PPh3)2 (14 mg, 0.020 mmol), Cul (12 mg, 0.063 mmol) and toluene

(20 mL). DBU (1.0 mL) was added dropwise to this stirred solution. Toluene (10 mL) was

added after 20 min and 30 min. After 20 h, the mixture was filtered, and the solid was

washed several times with warm toluene. The combined filtrate was concentrated to 40 mL

and was then dropped into methanol (200 mL). The white precipitate was collected and

reprecipitated in methanol from THF (40 mL) solution. The precipitate was dried under

vacuum at 65°C for 24 h to give 17 (0.48 g, 79%). UV (THF, nm): X^ = 270,316,366; BR

(cm*1): 1601,1629,2853,2925,2952,3049; ^-NMR: 8 0.81 (3 H, br.), 1.22-1.25 (10 H,

br., m.), 1.75 (2H, br.), 4.09 (2H, br.),7.23 (4H, d/8.5),7.64 (2H, d/8.5), 8.26 (4H, s);

"C-NMR: 8 14.1 (CH3), 22.6 (CH2), 27.2 (CH2), 28.9 (CH2), 29.2 (CH2), 29.3 (CH2), 31.8

(CH2), 43.1 (CH2), 89.0 (2 sp-C), 108.8 (2 sp2-CH), 114.3 (2 sp2-C), 122.5 (2 sp2-C), 123.8

(2 sp2-CH), 129.5 (2 sp2-CH), 140.0 (2 sp2-C); GPC: Mn = 1.19 x 104, Mw = 4.43 x 104, MJ

Mn = 3.73,1V = 0.21 dl/g.

80

Polymer 18

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 3,6-diethynyl-N-octylcarbazole (0.33 g, 1 mmol), 4,4'-diiodo-N-octylcarbazole

(0.50 g, 1 mmol), PdCl2(PPh3)2 (14 mg, 0.020 mmol), Cul (10 mg, 0.053 mmol) and toluene

(20 mL). l,8-Diazabicyclo[5.4.0]undec-7-ene DBU (1.0 mL) was added dropwise to this

stirred solution. Toluene (10 mL) was added after 10 min and 30 min. After 20 h, the

mixture was filtered and the solid was washed several times with warm toluene. The

combined filtrate was concentrated to 40 mL and was then dropped into methanol (200 mL).

The brownish yellow precipitate was collected and reprecipitated in methanol from THF (40

mL) solution. The precipitate was dried under vacuum at 65°C for 24 h to give lg (0.49 g,

84%). UV (THF, n m ) : U = 270,314,368; BRfcm1): 1507,1598,2205,2853,2925,

2952,3037; XH-NMR: 8 0.87 (6 H, br.), 1.23-1.30 (16 H, br. m.), 1.67 (2 H, br.), 1.84 (2 H,

br.), 3.73 (2 H, br.), 4.24 (2 H, br.), 7.00 (4 H, d/7.5), 7.32 (2 H, d / 8.0), 7.48 (4 H, d /

7.5), 7.62 (2 H, d/8.0), 8.25 (2 H, s); 13C-NMR: 814.0 (CH3), 14.1 (CH3), 22.6 (CH2),

22.7 (CH2), 26.7 (CH2), 27.2 (CH2), 27.4 (CH2), 28.9 (CH2), 29.1 (CH2), 29.3 (CH2), 31.6

(CH2), 31.7 (CH2), 43.3 (CH2), 52.2 (CH2), 88.0 (2 sp-C), 89.7 (2 sp-C), 108.9 (2 sp2-CH),

114.2 (2 sp2-C), 116.2 (2 sp2-C) 120.6 (4 sp2-CH), 122.5 (2 sp2-C), 123.9 (2 sp2-CH), 129.5

(2 sp2-CH), 132.6 (4 sp2-CH), 140.2 (2 sp2-CH) 147.0 (2 sp2-C); GPC: Mn = 1.08 x 104, Mw

= 3.70 x 104, M J Mn = 3.41, IV = 0.24 dl/g.

81

4,4'-dicyano-N-hexyIdiphenyIamine,25

A mixture of 4,4'-diiododiphenylamine (14.68 g, 30 mmol) and copper cyanide (8.06

g, 90 mmol) in DMF (100 mL) was refluxed under Ar. After 48 h, the mixture was allowed

to cool to ambient temperature and was then added with 1M KOH solution (150 mL) and

ether (150 mL). The organic layer was separated and the aqueous was extracted with ether (2

x 100 mL). The combined organic layer was washed with water (2 x 200 mL) and was dried

over anhydrous Na2S04. The solvent was removed and the residue was eluted through a flash

silica gel column by methylene chloride/hexane, 50/50. The product was collected and the

solvent was removed. The obtained solid was crystallized from hexane and dried under

vacuum to yield 25 (7.10 g, 78%) as white needles, mp: 74.5-75.5°C, HDRES EI: calcd for

C20H21N3 303.1736, measured 303.1728; BR (cm'1): 1504,1554,1595,1612,2219,2858,

2930,2955,3046,3094; XH-NMR: 8 0.83 (3 H, t/7.0), 1.27 (6 H, m), 1.62 (2 H, qui/7.0),

3.74 (2 H, t/7.0), 7.04 (4 H, d/9.0), 7.52 (4 H, d/9.0); 13C-NMR: 8 13.8 (CH3), 22.4

(CH2), 26.4 (CH2), 27.1 (CH2), 31.3 (CH2), 52.2 (CH2), 104.7 (2 CN), 119.0 (4 sp2-C), 120.9

(2 sp2-CH), 133.5 (4 sp2-CH), 150.0 (2 sp2-C).

4,4'-diformyI-N-hexyIdiphenyIamine,26

A 250 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with a solution of 1M lithium aluminium hydride in ether (24 mL, 24 mmol). Ethyl

acetate (36 mL, 36 mmol) was added dropwise to this stirred solution at 3-7 °C. After 1 h at

0 °C, 4,4'-dicyano-N-hexyldiphenyl amine (3.03 g, 10 mmol) in ether (lOmL) was added

dropwise to the mixture. After an additional 1.5 h at 0 °C, the resulting yellow slurry was

82

then quenched with 1M sulfuric acid (50 mL). After 30 min the organic layer was separated

and the aqueous was extracted with ether (3 x 20 mL). The combined organic layer was

washed with saturated NaHC03 solution (30 mL) and cold water (3 x 30 mL) and was dried

over anhydrous Na2SC«4. The solvent was removed and the residue was eluted through a flash

silica gel column by gradient solvents, methylene chloride/ hexane, from 25/75 to 100/0. The

product was collected and the solvent was removed. The obtained yellow oil was dried under

vacuum to yield 26 (1.74 g, 56%). HIRES EI: calcd for C20H23NO2 309.1729, measured

309.1732; BR (cm'1): 1508,1561,1587,1607,1691,2730,2856,2928,2955,3069; XH-

NMR: 8 0.84 (3 H, t/7.0), 1.27 (6 H, m), 1.66 (2 H, qui/7.0), 3.81 (2 H, t/7.0), 7.12 (4

H, d/9.0), 7.78 (4H, d/9.0), 9.85 (2H, s); 13C-NMR: 813.9 (CH3), 22.5 (CH2), 26.5

(CH2), 27.4 (CH2), 31.4 (CH2), 52.5 (CH2), 120.6 (4 sp2-CH), 130.5 (2 sp2-C), 131.5 (4 sp2-

CH), 151.8 (2 sp2-C), 190.4 (2 sp2-CHO).

PoIy-4,4'-vinyIene-N-hexyldiphenylamine (Polymer 24)

Li a dry 250 mL round bottom flask equipped with a magnetic stirring bar and reflux

condenser, titaniumtetrachloride (6.14 g, 32.35 mmol) and THF (50 mL) were carefully mixed

at about -40°C. Zinc powder (4.23 g, 64.7 mmol) was added slowly and the mixture was

heated to reflux. The reflux was continued for 50 h. The mixture was allowed to cool to

ambient temperature and was quenched by 10% K2C03 solution. The resulting solution was

filtered through celite and washed several times with methylene chloride. The combined

filtrate was concentrated to 50 mL and was then dropped into methanol (200 mL). The

yellow precipitate was collected and reprecipitated in acetone from a THF solution. The

83

yellow precipitate was dried under vacuum at 65°C for 24 h to give the desired polymer (0.55

g, 35%). UV (THF, nm): X^ = 400; IR(citf1):1508,1599,2854,2926,2952,3025; *H-

NMR: 8 0.86 (3 H, br.), 1.28 (6 H, br.), 1.64 (2 H, br.), 3.68 (2 H br.), 6.93-6.96 (6 H, m),

7.38 (4 H, br. d); 13C-NMR: 8 14.0 (CH3), 22.6 (CH2), 26.7 (CH2), 27.4 (CH2), 31.6 (CH2),

52.3 (CH2), 120.9 (4 sp2-CH), 126.1 (2 sp2-CH), 127.2 (4 sp2-CH), 130.8 (2 sp2-C), 146.9 (2

sp2-C); GPC: Mn = 2.45 x 104, Mw = 1.28 x 10s, M»/M„ = 5.22, IV = 0.60 dl/g.

4-formyI-N-hexyldiphenylamine, 28

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with N-hexyldiphenylamine (2.53 g, 10 mmol), anhydrous dimemylformamide (1.60

g, 22 mmol) and 1,2-dichloroethane (25 mL). Phosphorusoxy chloride (3.37 g, 22 mmol) was

added dropwise to this stirred solution at 0°C. After the addition was completed, the mixture

was allowed to warm to room temperature. The mixture was then heated at 60°C for 4 h.

The reaction mixture was allowed to cool to room temperature before it was poured into a

precooled sturated sodium acetate solution (100 mL, 0 °C). The organic layer was separated

and the aqueous layer was extracted with ether (2 x 30 mL). The combined organic layer was

washed with water (50 mL) followed by saturated NaHC03 solution (2 x 50 mL) and was

dried over anhydrous Na2S04. The solvent was removed to yield the product (2.68g, 95%) as

a yellow oil. This crude product was quite pure (>95% purity). However, further purification

was done by flash chromatography using silica gel column and ethylacetate/ hexane (10/90)

eluent HBRES EI: calcd for Ci9H23NO 281.1780, measured 281.1773; BR (cm'1): 1514,

1586,1602,1684,2694,2728,2807,2857,2928,2955,3030, 306; -NMR: 8 0.86 (3 H, t

84

/6.5), 1.28 (6 H, m), 1.68 (2 H, qui/7.5), 3.70 (2H, t/7.5), 6.68 (2 H, d/9.0), 7.19 (2 H,

d/7.5), 7.26 (H, t/7.5), 7.42 (H, t/7.5), 7.64 (2H, d/9.0), 9.71 (H, s); 13C-NMR: 8

13.9 (CH3), 22.5 (CH2), 26.5 (CH2), 27.1 (CH2), 31.5 (CH2), 52.6 (CH2), 113.2 (2 sp2-CH),

126.2 (sp2-C), 126.4 (sp2-CH), 127.5 (2 sp2-CH), 130.0 (2 sp2-Q, 131.7 (2 sp2-CH), 145.6

(sp2-C), 153.3 (sp2-C), 190.1 (sp2-CHO).

dimer 27

The synthesis of dimer 27 from a reductive McMurry coupling reaction of 4-f ormyl-N-

hexyldiphenylamine was performed in the same fashion as the polymerization of the diformyl

monomer 26 to form polymer 24. Yield: 55%; *H-NMR: 8 0.86 (6 H, t/7.0), 1.27 (12 H,

m.), 1.64 (4 H, qui. / 7.0), 3.65 (4 H t / 7.0), 6.88-6.95 (8 H, m), 7.00 (4 H, d / 9.0), 7.22 (4

H, t / 9.0), 7.32 (4 H, d / 9.0); 13C-NMR: 8 14.0 (2 CH3), 22.6 (2 CH2), 26.7 (2 CH2), 27.4

(2 CH2), 31.5 (2 CH2), 52.2 (2 CH2), 119.8 (4 sp2-CH), 121.6 (2 sp2-CH), 121.7 (4 sp2-CH),

125.8 (2 sp2-CH), 127.0 (4 sp2-CH), 129.2 (4 sp2-CH), 130.1 (2 sp2-C), 147.0 (2 sp2-C);

147.7 (2 sp2-C).

4,4',4"-triiodotriphenyIamine, TI3

A 500 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with triphenylamine (7.36 g, 30 mmol), chloroform (100 mL) and methanol (50 mL).

BTMAIC12 (34.47 g, 99 mmol) and CaC03 (18 g, 0.18 mol) was added quickly to this stirred

solution. After 72 h of reflux, 20% NaHS03 solution was added to the mixture until the

mixture became light green. The mixture was filtered and the filtrate was separated. The

85

aqueous layer was extracted with methylene chloride (2 x 50 mL). The combined organic

layer was washed with water (2 x 100 mL) and dried over anhydrous MgS04. The mixture

was concentrated and the residue was eluted through a flash silica gel column by hexane. The

solvents was removed and the resulting yellow oil was dried under vacuum at 65 °C for 24 h

to give TI3 (12.30 g, 66%). XH-NMR: 8 6.80 (6 H, d/9.0), 7.52 (6 H, d/9.0), 13C-NMR:

8 86.6 (3 sp2-C), 126.0 (6 sp2-CH), 138.4 (6 sp2-CH), 146.5 (3 sp2-C).

4-trimethyIsilyIethynyl-N,N,-dimethylaniline, (SiEAMe2)

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 4-iodo-N,N-dimethylaniline (2.47 g, 10 mmol), PdCl2(PPh3)2 (30 mg), Cul (19

mg), DBU (1.64 g) and toluene (30 mL). Trimethylsilylacetylene (1.08g, 11 mmol). was

added dropwise to this stirred solution. After 2 h, the mixture was filtered and the precipitate

was washed with toluene (3 x 15 mL). The combined filtrate was concentrated and the

residue was eluted through a short alumina column by methylene chloride. The solvent was

removed and the resulting yellow solid was dried under vacuum for 24 h to give the desired

product (1.91 g, 88 %). The product was characterized only by GC-1R-MS. BR (cm'1):

1515,2150,2806,2963; MS: 217 (M*), 202 (100%), 186,172,158,101.

4-ethynyI-N,N-dimethylaniIine, EAMe2

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with trimemylsUylemynyl-N,N-dimethylaniline (1.5 g) and methanol (20 mL).

Saturated KOH aqueous solution (0.2 mL) was added dropwise to this stirred solution. After

86

6 h, potassium bicarbonate solution (10%, 20 mL) and hexane (20 mL) was added to the

mixture. The organic layer was separated and the aqueous layer was extracted with hexane (2

x 20 mL). The combined organic layer was washed with water (2 x 20 mL) and was then

dried over anhydrous MgS04. The solvent was removed and the resulting yellow solid was

dried under vacuum for 24 h to give EAMe2 (1.00 g, 95%). m.p.: 50-51 °C; HBRES EI: clcd

for CioHuN 145.0892, measured 145.0891; UV (CHCI3, nm): 292; BR^m'1): 1516,1605,

2814,2895,2097,3266; XH-NMR (CD3CN): 8 2.93 (6 H, s), 3.19 (H, s), 6.65 (2 H, d /

9.0), 7.30 (2 H, d/9.0); 13C-NMR (CD3CN): 840.2 (2 CH3), 76.2 (sp-CH), 85.3 (sp-C),

109.0 (sp2-C), 112.6 (2 sp2-CH), 133.7 (2 sp2-CH), 151.5 (sp2-C).

4,4',4"-Tris-(4-dimethylaminophenyIethynyl)triphenyIamine, GO

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 4,4^4''-tiTiodotriphenylarnine (0.62 g, 1 mmol), PdCl2(PPh3)2 (10 mg, 0.014

mmol), Cul (5 mg 0.026 mmol), 4-ethynyl-N,N-dimethylaniline (0.44 g, 3 mmol), toluene (20

mL) and THF (10 mL). DBU (0.5 mL) was added dropwise to this stirred solution. After 24

h, methanol (30 mL) was added to the mixture and was then filtered. The obtained yellow

solid was reprecipitated in methanol from methylene chloride solution. The precipitate was

dried under vacuum for 24 h to give GO (0.56 g, 83 %). DSC( rt-400 °C, rate 20 °C/min):

endothermic at 133-152°C (144°C), exothermic at 152-171 °C (157 °C), m.p.range 268-287

°C (278 °C); m.p.: 267-269 °C; HIRES EI: GusH^N, 674.3410, measured 674.3414;

BRtcm-1): 1501,1523,1609,2208,2803,2890, 3037; UV (THF, nm): A ^ =378; JH-NMR

(CD3CN): 8 2.98 (18 H, s), 6.66 (6 H, d / 9.0), 7.04 (6 H, d / 9.0), 7.40 (6 H, d / 9.0), 7.41

87

(6 H, d/9.0); 13C-NMR (CD3CN): 840.1 (3 CH3), 87.2 (3 sp-C), 90.3 (3 sp-C), 110.1 (3

sp2-C), 111.8 (6 sp2-CH), 118.6 (3 sp2-Q, 123.8 (6 sp2-CH), 132.3 (6 sp2-CH), 132.5 (6 sp2-

CH), 146.1 (3 sp2-C), 149.9 (3 sp2-Q.

4-iodo-N,N-dibutyIaniline, IABu2

A 500 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with triphenylamine (10.27 g, 50 mmol) CaC03 (15.02 g, 0.15 mol) and methylene

chloride (50 mL). A solution of BTMAIC12 (18.11 g, 52 mmol) in methylene chloride/

methanol (80 mL/100 mL) was added dropwise to this stirred solution. After 24 h, 20%

NaHS03 solution was added to the mixture until the mixture became light purple. The

mixture was filtered and the filtrate was separated. The aqueous layer was extracted with

methylene chloride (2 x 50 mL). The combined organic layer was washed with water (2 x

100 mL) and dried over anhydrous MgS04. The mixture was concentrated and the residue

was eluted through a flash silica gel column by hexane. The solvents was removed and the

resulting yellow oil was dried under vacuum at 65 °C for 24 h to give IABu2 (15.06 g, 91%).

XH-NMR: 8 0.94 (6 H, t/7.5), 1.32 (4H, sex/7.5), 1.52 (4 H, qui/7.5), 3.21 (2 H, t /

7.5), 6.40 (2H, d/9.0), 7.40 (2H, d/9.0); 13C-NMR: 8 14.0 (2CH3),20.3 (2CH2),29.2

(2 CH2), 50.7 (2 CH2), 75.3 (sp2-C), 114.0 (2 sp2-CH), 137.6 (2 sp2-CH), 147.6 (sp2-C).

4-ethynyl-N,N,-dibuthylaniIine,EABu2

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 4-iodo-N,N-dibutylaniline (15.0 g, 45.3 mmol), PdCl2(PPh3)2 (100 mg, 0.142

88

mmol), Cul (50 mg, 0.263 mmol), trimethylsilyl acetylene (4.50 g, 45.8 mmol) and toluene

(30 mL). DBU (7.0 mL) was added dropwise to this stirred mixture. After 24 h, the mixture

was filtered and the solid was washed with toluene (3 x 15 mL). The combined filtrate was

concentrated and the residue was eluted through a flash silica gel column by hexane. The

solvent was removed and the resulting yellow oil was dried under vacuum for 24 h to give 4-

trimemylsUylemynyl-N^-dibutylaminobenzene. This trimemylsUylemynyl-N^-dibutylaniline

was dissolved in methanol (200 mL) and was flushed with Ar (to avoid a possible oxidative

coupling reaction). Saturated KOH aqueous solution (0.5 mL) was added dropwise to this

solution. After 12 h, water (100 mL) and hexane (50 mL) was added to the mixture. The

organic layer was separated and the aqueous layer was extracted with hexane (2 x 50 mL).

The combined organic layer was washed with water (2 x 50 mL) and was then dried over

anhydrous MgS04. The solvent was removed and the resulting yellow oil was dried under

vacuum for 24 h to give EABu2 (9.70 g, 93%). HBRES EI: calcd for QeHasN 229.1833,

measured 229.1830; BR^m1): 1516,1608,2099,2931,2957,3043,3094, 3307; ^-NMR:

80.96 (6 H, t/7.5), 1.35 (4H, sex/7.5), 1.56 (4H, qui/7.5), 2.96 (H, s), 3.27 (4H, t /

7.5), 6.54 (2 H, d / 9.0), 7.33 (2 H, d / 9.0); 13C-NMR: 8 13.9 (2 CH3), 20.2 (2 CH2), 29.2

(2 CH2), 50.6 (2 CH2), 74.3 (sp-CH), 85.0 (sp-C), 107.3 (sp2-C), 111.0 (2 sp2-CH), 133.3 (2

sp2-CH), 148.1 (sp2-C).

4,4'-diiodo-4''-trimethyIsilylethynyItriphenyIamine, SiETI2

A 500 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with of 4,4',4"-triiodotriphenylamine (24.00 g, 38.5 mmol), PdCl2(PPh3)2 (68 mg,

89

0.097 mmol), Cul (34 mg, 0.18 mmol),rrimethylsilyl acetylene (4.54 g, 46 mmol) and toluene

(200 mL). DBU (7 mL, 46 mmol) was added dropwise to this stirred solution. After 24 h,

the mixture was filtered and the solid was washed with toluene (3 x 30 mL). The combined

filtrate was concentrated and the residue was eluted through a flash silica gel column by

hexane. The product was collected and the solvent was removed. The resulting white solid

was dried at 65 °C under vacuum for 24 h to give SiETI2 (9.54 g, 43%). HBRES EI: calcd

for CaHbNfcSi (M+H) 593.9611, measured 593.9619; ERfcin1): 1483,1503,1583,2153,

2956,3035; *H-NMR: 8 0.23 (9 H, s), 6.80 (4 H, d / 8.5), 6.93 (2 H, d / 8.5), 7.20 (2 H, d /

8.5), 7.52 (2 H, d/8.5); 13C-NMR: 80.03 (3 CH3), 86.8 (sp2-C), 93.9 (sp-C), 104.8 (sp-C),

117.5 (2 sp2-C), 123.1 (2 sp2-CH), 126.3 (4 sp2-CH), 133.2 (2 sp2-CH), 138.4 (4 sp2-CH),

146.5 (2 sp2-C), 146.8 (sp2-C).

4"-trimethylsiIyIethynyl-4,4'-bis-(4-N,N-dibutyIaminophenylethynyl) triphenyl amine,

SiET(EABu2)2

A 250 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with SiETI2 (5.80 g, 10.0 mmol), PdCl2(PPh3)2 (50 mg, 0.071 mmol), Cul (25 mg,

0.13 mmol), 4-dibutylaminoethynylbenzene (5.04 g, 22 mmol) and toluene (75 mL). DBU

(4.0 mL, 27 mmol) was added dropwise to this stirred solution. After 36 h, the mixture was

filtered and the solid was washed with toluene (3 x 30 mL). The combined filtrate was

evaporated and the residue was eluted through a flash silica gel column by gradient solvents

from pure hexane to methylene chloride/hexane (30/70). The product was collected and the

solvent was removed. The resulting yellow solid was dried at 65 °C under vacuum for 24 h.

90

to give SiET(EABu2)2 (6.10 g, 77%). *H-NMR: 8 0.29 (9 H, s), 0.99 (12 H, t/7.5), 1.38

(8 H, sex /7.5), 1.58 (8 H, qui / 7.5), 3.29 (8 H, t / 7.5), 6.59 (4 H, d / 9.0), 7.00 (2 H, d /

8.5), 7.02 (4 H, d/8.5), 7.36-7.42 (10 H, m); 13C-NMR: 8 0.07 (3 CH3), 13.9 (4 CH3), 20.2

(4 CH2), 29.3 (4 CH2), 50.5 (4 CH2), 86.8 (2 sp-C), 90.7 (2 sp-C), 93.3 (sp-C), 105.1 (sp-C),

108.8 (2 sp2-C), 111.1 (4 sp2-CH), 117.0 (sp2-C), 119.1 (2 sp2-C), 123.0 (2 sp2-CH), 124.0 (4

sp2-CH), 132.2 (4 sp2-CH), 132.6 (4 sp2-CH), 132.9 (2 sp2-CH), 145.6 (2 sp2-C), 147.0 (sp2-

C), 147.6 (2 sp2-C).

4"-ethynyl-4,4'-bis-(4-N,N-dibutylaminophenyIethynyI)triphenylamine, ET(EABu2)2

A 250 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with SiET(EABu2)2 (2.50 g, 5.7 mmol), THF (50 mL) and methanol (50 mL).

Saturated KOH aqueous solution (0.5 mL) was added dropwise to this stirred solution. After

6 h, water (30 mL) and hexane (30 mL) was added to the mixture. The organic layer was

separated and the aqueous layer was extracted with methylene chloride (2 x 30 mL). The

combined organic layer was washed with water (2 x 30 mL) and was then dried over

anhydrous MgSO*. The solvent was removed and the resulting yellow solid was dried under

vacuum for 24 h to give ET(EABu2)2 (4.02 g, 98%). XH-NMR: 8 0.99 (12 H, t/7.5), 1.35

(8 H, sex/7.5), 1.59 (8 H, qui/7.5), 3.06 (H, s), 3.30 (8 H, t/7.5), 6.60 (4H, d/9.0),

7.03 (2 H, d / 8.5), 7.05 (4 H, d / 8.5), 7.36-7.42 (10 H, m); "C-NMR: 8 14.0 (4 CH3), 20.2

(4 CH2), 29.3 (4 CH2), 50.6 (4 CH2), 76.6 (sp-CH), 83.6 (sp-C), 86.8 (2 sp-C), 90.7 (2 sp-C),

108.7 (2 sp2-C), 111.1 (4 sp2-CH), 115.8 (sp2-C), 119.2 (2 sp2-C), 123.1 (2 sp2-CH), 124.1 (4

sp2-CH), 132.3 (4 sp2-CH), 132.7 (4 sp2-CH), 133.1 (2 sp2-CH), 145.7 (2 sp2-C), 147.4 (sp2-

91

C), 147.7 (2 sp2-C)

Gl

A 50 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with ET(EABu2)2 (0.60 g, 0.83 mmol), PdCl2(PPh3)2 (10 mg, 0.014 mmol), Cul (5

mg, 0.026 mmol), 4,4^4''-triiodotriphenylamine (0.17 g, 0.27 mmol) and toluene (10 mL).

DBU (0.20 mL, 1.4 mmol) was added dropwise to this stirred solution. After 36 h, the

mixture was filtered and the solid was washed with toluene (3 x 10 mL). The combined

filtrate was concentrated to 10 mL and was then dropped into 200 mL methanol. The

obtained yellow precipitate was eluted through a flash silica gel column by methylene

chloride/hexane (40/60). The product was collected and the solvent was removed. The

resulting yellow solid was dried at 65 °C under vacuum for 24 h to give Gl (0.610 g, 93%).

EI Mass: calcd for G74H180N10 2411.45, measured 2411.47; BR(cm_1): 1513,1519,1606,

2150,2207,2870,2929,2958,3037, 3090; UV (THF, nm): X^ = 386; XH-NMR: 8 0.95

(36 H, t / 7.5), 1.35 (24 H, sex / 7.5), 1.58 (24 H, qui / 7.5), 3.27 (24 H, t / 7.5), 6.57 (12 H,

d/9.0), 7.02-7.07 (24 H, m), 7.33-7.42 (36 H, m); 13C-NMR: 8 14.0 (12 CH3), 20.3 (12

CH2), 29.3 (12 CH2), 50.5 (12 CH2), 86.8 (6 sp-C), 88.9 (3 sp-C), 89.3 (3 sp-C), 90.6 (6 sp-

C), 108.8 (6 sp2-C), 111.2 (12 sp2-CH), 117.4 (3 sp2-C), 118.1 (3 sp2-C), 119.0 (6 sp2-C),

123.5 (6 sp2-CH), 124.0 (6 sp2-CH), 124.1 (12 sp2-CH), 132.3 (12 sp2-CH), 132.6 (6 sp2-

CH), 132.7 (6 sp2-CH), 132.8 (12 sp2-CH), 145.9 (6 sp2-Q, 146.5 (3 sp2-C), 146.8 (3 sp2-C),

147.8 (6 sp2-C); GPC: Mn = 2.40 x 103, Mw = 2.47 x 103, M J Mn = 1.03, IV = 0.08 dl/g;

DSC: no transition before an exothermic transition (crosslinking) at 300°C

92

SiET[ET(EABu2)2]2

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with ET(EABu2)2 (4.02 g, 5.6 mmol), PdCl2(PPh3)2 (40 mg, 0.057 mmol), Cul (20

mg, 0.11 mmol), SiETI2 (1.38 g, 2.32 mmol) and toluene (30 mL). DBU (0.90 mL, 6.1

mmol) was added dropwise. After 36 h, the mixture was filtered and the solid was washed

with toluene (3 x 30 mL). The combined filtrate was evaporated to dryness. The residue was

eluted through a flash silica gel column by gradient solvents, from pure hexane to methylene

chloride/hexane (35/65). The product was collected and the solvent was removed. The

resulting yellow solid was dried at 65 °C under vacuum for 24 h. to give SiET[ET(EABu2)2]2

(2.90 g, 70%). XH-NMR: 8 0.26 (9 H, t/7.5), 0.97 (24 H, t/7.5), 1.36 (16 H, sex/7.5),

1.58 (16 H, qui/7.5), 3.28 (16 H, t/7.5), 6.57 (8 H, d/9.0), 7.01-7.06 (18 H, m), 7.34-

7.42 (26 H, m); 13C-NMR: 8 0.0 (3 CH3), 14.0 (8 CH3), 20.3 (8 CH2), 29.3 (8 CH2), 50.6 (8

CH2), 86.8 (4 sp-C), 88.8 (2 sp-C), 89.3 (2 sp-C), 90.6 (4 sp-C), 93.8 (sp-C), 104.9 (sp-C),

108.8 (4 sp2-C), 111.1 (8 sp2-CH), 117.3 (2 sp2-C), 117.5 (sp2-C), 118.2 (2 sp2-C), 119.0 (4

sp2-C), 123.4 (4 sp2-CH), 123.7 (2 sp2-CH), 124.0 (4 sp2-CH), 124.1 (8 sp2-CH), 132.3 (8

sp2-CH), 132.5 (4 sp2-CH), 132.6 (4 sp2-CH), 132.7 (8 sp2-CH), 133.1 (2 sp2-CH), 145.8 (4

sp2-C), 146.4 (2 sp2-C), 146.8 (2 sp2-C), 146.9 (sp2-C), 147.8 (4 sp2-C).

ET[ET(EABu2)2]2

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with SiET[ET(EABu2)2]2 (2.70 g, 1.5 mmol), THF (30 mL) and methanol (20 mL).

Saturated KOH aqueous solution (0.2 mL) was added dropwise to this stirred solution. After

93

6 h, the mixture was added with water (30 mL) and hexane (30 mL). The organic layer was

separated and the aqueous layer was extracted with methylene chloride (2 x 30 mL). The

combined organic layer was washed with water (2 x 30 mL) and was then dried over

anhydrous MgS04. The solvent was removed and the resulting yellow solid was dried under

vacuum for 24 h. to give ET[ET(EABu2)2]2 (2.55 g, 98%). 'H-NMR: 8 0.97 (24 H, t/7.5),

1.36 (16 H, sex/7.5), 1.58 (16 H, qui/7.5), 3.28 (16 H, t/7.5), 6.57 (8 H, d/9.0),7.03-

7.06 (18 H, m), 7.34-7.43 (26 H, m); "C-NMR: 8 14.0 (8 CH3), 20.3 (8 CH2), 29.3 (8 CH2),

50.6 (8 CH2), 76.8 (sp-C), 83.5 (sp-C), 86.8 (4 sp-C), 88.8 (2 sp-C), 89.3 (2 sp-C), 90.6 (4

sp-C), 108.8 (4 sp2-C), 111.1 (8 sp2-CH), 116.4 (sp2-C), 117.3 (2 sp2-C), 118.3 (2 sp2-C),

119.0 (4 sp2-C), 123.4 (4 sp2-CH), 123.6 (2 sp2-CH), 124.0 (4 sp2-CH), 124.1 (8 sp2-CH),

132.3 (8 sp2-CH), 132.5 (4 sp2-CH), 132.6 (4 sp2-CH), 132.7 (8 sp2-CH), 133.3 (2 sp2-CH),

145.8 (4 sp2-C), 146.3 (2 sp2-C), 146.8 (2 sp2-C), 147.2 (sp2-C), 147.8 (4 sp2-C).

G2

A 250 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with ET[ET(EABu2)2]2 (0.78 g, 0.43 mmol), PdCl2(PPh3)2 (10 mg, 0.014 mmol),

Cul (5 mg, 0.026 mmol), 4,4',4"-triiodotriphenylamine (80 mg, 0.13 mmol) and toluene (10

mL). DBU (0.10 mL, 0.70 mmol) was added dropwise to this stirred solution. After 36 h,

the mixture was filtered and the solid was washed with toluene (3 x 10 mL). The combined

filtrate was concentrated to 10 mL and was then dropped into 200 mL methanol. The

obtained yellow precipitate was eluted through a flash silica gel column by gradient solvents,

methylene chloride/hexane, from 20/80 to 45/55. The product was collected and the solvent

94

was removed. The resulting yellow solid was dried at 65 °C under vacuum for 24 h. to give

G2 (0.50 g, 73%). MALDI Mass: calcd for C39oH384N22 5379, measured 5374; UV (THF,

n r n ) : U = 386; XH-NMR: 8 0.96 (72H, t/7.5), 1.35 (48 H, sex/7.5), 1.57 (48 H, qui /

7.5), 3.27 (48 H, t/7.5), 6.57 (24 H, d/9.0), 7.03-7.08 (60 H, m), 7.33-7.43 (84H, m);

13C-NMR: 8 14.0 (24 CH3), 20.3 (24 CH2), 29.3 (24 CH2), 50.6 (24 CH2), 86.8 (12 sp-C),

88.9 (6 sp-C), 89.1 (3 sp-C), 89.2 (3 sp-C), 89.3 (6 sp-C), 90.6 (12 sp-C), 108.8 (12 sp2-C),

111.1 (24 sp2-CH), 117.4 (6 sp2-C), 117.9 (3 sp2-C), 118.0 (3 sp2-C), 118.1 (6 sp2-C), 119.0

(12 sp2-C), 123.5 (12 sp2-CH), 123.9 (6 sp2-CH), 124.0 (18 sp2-CH), 124.1 (24 sp2-CH),

132.3 (24 sp2-CH), 132.5 (12 sp2-CH), 132.6 (24 sp2-CH), 132.7 (24 sp2-CH), 145.9 (12 sp2-

C), 146.4 (6 sp2-C), 146.5 (3 sp2-C), 146.6 (3 sp2-C), 146.8 (6 sp2-C), 147.8 (12 sp2-C);

GPC: Mn = 5.21 x 103, Mw = 5.25 x 103, M J Mn = 1.01, IV = 0.12 dl/g; DSC: no transition

before an exothermic transition (crosslinking) at 300°C

SiET[ET[ET(EABu2)2]2]2

A 250 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with ET[ET(EABu2)2]2 (2.50 g, 1.46 mmol), PdCl2(PPh3)2 (20 mg, 0.028 mmol),

Cul (10 mg, 0.052 mmol) and4''-trimemylsUylemynyl-4,4'-dh^otriphenylamine (0.35 g, 59

mmol) in toluene (20 mL) under Ar was added dropwise, DBU (0.25 mL, 1.7 mmol). After

48 h. the mixture was filtered and the solid was washed with toluene (3 x 20 mL). The

combined filtrate was concentrated to 20 mL and was then dropped into 200 mL methanol.

The obtained yellow precipitate was eluted through a flash silica gel column by gradient

solvents from methylene chloride/hexane (15/85) to (40/60). The product was collected and

95

the solvent was removed. The resulting yellow solid was dried at 65 °C under vacuum for 24

h. to give SiET[ET[ET(EABu2)2]2]2 (1.80 g, 81%). 'H-NMR: 8 0.26 (9 H, s), 0.96 (48 H, t

/7.5), 1.36 (32H, sex/7.5), 1.57 (32H, qui/7.5), 3.28 (32H, t/7.5), 6.57 (16 H, d /

9.0), 7.03-7.08 (42 H, m), 7.34-7.43 (58 H, m); 13C-NMR: 8 13.99 (16 CH3), 20.2 (16 CH2),

29.1 (16 CH2), 50.6 (16 CH2), 77.2 (sp-CH), 83.5 (sp-C), 86.8 (8 sp-C), 88.9 (4 sp-C), 89.0

(2 sp-C), 89.2 (2 sp-C), 89.3 (4 sp-C), 90.7 (8 sp-C), 108.8 (8 sp2-C), 111.1 (16 sp2-CH),

116.5 (sp-C), 117.4 (4 sp2-C), 104.9 (sp-C), 117.6 (sp2-C), 117.9 (2 sp2-C), 118.0 (2 sp2-C),

118.1 (4 sp2-C), 119.0 (8 sp2-C), 123.4 (8 sp2-CH), 123.8 (2 sp2-CH), 123.9 (4 sp2-CH),

124.0 (12 sp2-CH), 124.1 (16 sp2-CH), 132.3 (16 sp2-CH), 132.5 (8 sp2-CH), 132.6 (16 sp2-

CH), 132.7 (16 sp2-CH), 133.1 (2 sp2-CH), 145.9 (8 sp2-C), 146.4 (5 sp2-C), 146.6 (2 sp2-C),

146.8 (4 sp2-C), 146.9 (2 sp2-C), 147.8 (8 sp2-C).

ET[ET[ET(EA)2]2]2

Into a stirred solution of SiET[ET[ET(EA)2]2]2 (1.80 g, 0.42 mmol) in THF/methanol

(30 mL/12 mL) under Ar was added dropwise, saturated KOH aqueous solution (0.1 mL).

After 6 h, water (30 mL) and hexane (30 mL) were added to the mixture. The organic layer

was separated and the aqueous layer was extracted with methylene chloride (2 x 30 mL). The

combined organic layer was washed with water (2 x 30 mL) and was then dried over

anhydrous MgS04. The solvent was removed and the resulting yellow solid was dried under

vacuum for 24 h to give ET[ET[ET(EA)2]2]2 (1.74 g, 99%). XH-NMR: 8 1.00 (48 H, t /

7.5), 1.38 (32 H, sex/7.5), 1.60 (32H, qui/7.5), 3.08 (H, t/7.5), 3.30 (32 H, t/7.5),

6.60 (16 H, d/9.0), 7.05-7.08 (42H, m), 7.37-7.45 (58 H, m); 13C-NMR: 8 14.0 (16 CH3),

96

20.3 (16 CH2), 29.3 (16 CH2), 50.6 (16 CH2), 77.2 (sp-C), 83.5 (sp-C), 86.8 (8 sp-C), 88.9 (4

sp-C), 89.0 (2 sp-C), 89.2 (2 sp-C), 89.3 (4 sp-C), 90.6 (8 sp-C), 108.8 (8 sp2-C), 111.1 (16

sp2-CH), 116.5 (sp2-C), 117.3 (4 sp2-C), 117.8 (2 sp2-Q, 118.1 (6 sp2-C), 119.0 (8 sp2-C),

123.4 (8 sp2-CH), 123.6 (2 sp2-CH), 123.8 (4 sp2-CH), 124.0 (12 sp2-CH), 124.0 (16 sp2-

CH), 132.3 (16 sp2-CH), 132.5 (8 sp2-CH), 132.6 (12 sp2-CH), 132.7 (20 sp2-CH), 133.2 (2

sp2-CH), 145.8 (8 sp2-Q, 146.3 (6 sp2-C), 146.5 (2 sp2-C), 146.7 (4 sp2-C), 147.1 (sp2-C),

147.7 (8 sp2-C).

G3

Into a stirred solution of ET[ET[ET(EA)2]2]2 (1.742 g, 0.47 mmol), PdCl2(PPh3)2 (25

mg, 0.035 mmol), Cul (10 mg, 0.052 mmol) and 4,4',4"-triiodotriphenylamine (82 mg, 0.13

mmol) in toluene (20 mL) under Ar was added dropwise, DBU (0.20 mL, 1.4 mmol). After

72 h, the mixture was filtered and the precipitate was washed with toluene (3 x 10 mL). The

combined filtrate was concentrated to 10 mL and was then dropped into 200 mL methanol.

The obtained yellow precipitate was eluted through a flash silica gel column by gradient

solvents, methylene chloride/hexane, from 20/80 to 60/40. The product was collected and the

solvent was removed. The resulting yellow solid was dried at 65 °C under vacuum for 24 h.

to give an inseparable mixture of di- and tri- substituted products. "'H-NMR: 8 0.97 (144 H, t

/7.5), 1.34 (96 H, sex/7.5), 1.58 (96 H, qui/7.5), 3.29 (H, t/7.5); 6.58 (48 H, d/9.0),

7.04-7.09 (132 H, m), 7.37-7.45 (180 H, m); 13C-NMR: 8 14.0 (48 CH3), 20.3 (48 CH2),

29.3 (16 CH2), 50.6 (16 CH2), 86.8 (24 sp-C), 88.9 (12 sp-C), 89.0 - 89.2 (18 sp-C), 89.3 (12

sp-C), 90.6 (24 sp-C), 108.8 (24 sp2-C), 111.1 (48 sp2-CH), unassigned aromatic carbon

peaks from 117.3-132.7,145.8 (24 sp2-C), 146.2 (3 sp2-C), 146.4 (12 sp2-C), 146.5-146.7

(15 sp2-C), 146.8 (12 sp2-C), 147.7 (24 sp2-C); GPC: bimodal with Mn = 1.03 x 104, Mw =

1.08 x 104, MJM n = 1.04, IV = 0.14 dl/g.

97

PARTH

REACTION OF ELECTRON-RICH ACETYLENES WITH

TETRACYANOETHYLENE (TCNE)

98

INTRODUCTION

Introductory Remarks

Interest in organic electron donor-acceptor (EDA) complexes has increased

considerably over the past four decades due greatly to the involvement of EDA complexation

in numerous organic reactions and biochemical processes. EDA complexes are particularly

important in the pioneering work on electrical conductivity of organic compounds. These

studies initiated one of the most exciting subjects in materials chemistry; electrically

conducting polymers.1 Organic polymers are normally electrical insulators, but in certain

polymers the conductivity can be greatly increased by doping, adding electron acceptors (p-

dopants) or electron donors (n-dopants) to the polymers.2 The dopants form EDA complexes

with the polymers which can be observed by UV-Vis or near-IR spectroscopy.

Our design and synthesis of new series of N-interrupted polyphenyleneethynylene was

originally intended for electrical conductivity and electroluminescent studies as specified in the

previous chapter. Nevertheless, the study of EDA complexation by UV-Vis spectroscopy of

various organic acceptors with this new class of polymers has led us to a discovery of a

convenient route to synthesize electron donor-acceptor molecules of interest as second-order

nonlinear optical (NLO) chromophores. Polymers containing these NLO chromophores

arealso interesting as second harmonic generator (SHG) materials. This part of the thesis will

be devoted to the discussion of this discovery and the application of this reaction with various

electron-rich acetylenes.

99

Donor-Acceptor Complexes

Foster3 defined electron donor-acceptor (EDA) complexes (also often referred to as

charge-transfer complexes) as "a substance formed by the interaction of two or more

component molecules (and/ or ions), which may have an independent crystal structure and

which reversibly dissociate into its components, at least partially, in vapor phase and solution.

This definition suggests that there is very little or no contribution from covalent binding in the

ground state. However, there is a gradation from these weaker interactions to classical

covalent bond formation". The interaction between an electron donor (D) and an electron

acceptor (A) at ground state can be described in terms of a wave function of the form:4a

yN(AD) = a \j/o(A,D) + b yi(A"-D+) (1)

where: a2 + 2 abyoYi + b2 = 1

and at the corresponding excited state can be described as:

\|%(AD) = a* yi(A--D+) - r / \|fo(A,D) (2)

where: a"2 - 2 aVyoYi + b"2 = 1

Two extreme cases of EDA complexes are molecular complexes and ionic

complexes.43 According to equation (1), an EDA complex is a molecular complex when a »

b and it is an ionic complex when b » a. In the molecular complexes, also often called weak

complexes, the interaction between a donor and acceptor is a weak intermolecular force such

as a dipole-dipole, dipole-induced-dipole, London dispersion force or hydrogen bonding.

There is also very little or no transfer of charge in the molecular complexes in the ground

100

state. This type of complex possesses most of the individual molecular character of its

components; the donor and the acceptor. The molecular character can be observed through

the IR spectra of these complexes which are almost identical to the sum of the IR spectra of

their components.41' The ionic complexes are the other extreme where there is a completed or

almost completed transfer of an electron or electrons from donors to acceptors in the ground

state complexes. These complexes have the character of the cations of donors and the anions

of the acceptors which also can be observed by IR. Complexes which fall between these two

extremes are called strong complexes. The degree of complexation in solution depends on the

solvents, the donors, and acceptors. While the molecular complexes are commonly found in

poorly ionizing solvents, the ionic complexes are formed from low ionization energy donors

and high electron affinity acceptors in better ionizing solvents such as acetonitrile or ethanol.

An EDA complex can be observed spectroscopically (UV-Vis, IR, NMR and X-ray).

The simplest and most common technique is UV-Vis spectroscopy. Brackman40 observed that

a molecular complex still retains the electronic absorption of the components modified to a

greater or lesser extent, together with one or more absorption bands characteristic of the

complex as a whole. In practice, the absorption characteristics of the molecular complex in

solution may not be easily observed since the complex will be partially dissociated into its

components. This problem can sometimes be solved experimentally by making the optical

measurements at low temperatures or in the solid state which will favor complex formation.

The lowest absorption energy is usually the most important and is referred to as a charge-

transfer (CT) transition energy. The CT transition energy, ECT, depends on the ionization

101

potential of the donor, ID, and the electron affinity of the acceptor, EA. A plot of ECT for a set

of complexes of a series of donors with a given acceptor, against the ID of the donors is often

a straight line. This linear relationship is also often found for the plot of ECT for a set of

complexes of a series of acceptors with a given donor, against the EA of a series acceptors.

Thus, the CT transition energies can be described as the equations shown below.4*1

Ecr = 0lD + & (3)

where a and b are constant for a given acceptor and

Ecr = a'EA + b' (4)

where a' and b' are constant for a given donor.

Chemistry of aromatic monoamines with electron acceptors

Aromatic amines are good electron donors and can form EDA complexes with most

electron acceptors. In some cases, especially with strong electron acceptors, chemical

reactions may also occur.

Li poorly ionizing solvents, such as cyclohexane and carbon tetrachloride, aromatic

monoamines form molecular complexes with iodine3,4, p-benzoquinone5, tetracyanoethylene6

and halogenated organic compounds.7 In polar solvents, the amines can also form ionic

complexes with quinones, with a high electron affinity, such as chloranil. An ionic complex of

an amine usually appears as a pair of an amine radical cation with an acceptor radical anion

suggesting a single electron transfer between the donor and acceptor. Some experimental

102

results have indicated that the molecular complex is on the reaction path in the formation of

the radical-ion pair.8

Aromatic amines react with strong electron acceptors through the formation of

molecular and ionic EDA complexes in the first two steps. The reaction of N,N-

dimethylaniline (DMA) with chloranil in the absence of solvent is of particular interest in that

crystal violet, 1, is formed.9 The proposed mechanism is shown in Scheme 1. The molecular

complex in solution was observed by the electronic absorption at 650 nm immediately after

mixing. Upon mixing, no ESR absorption was observed, but with time, it increased to a

maximum at about three days and eventually disappeared. This ESR absorption corresponded

closely to the absorption of the chloranil semiquinone ion.

The other common reaction between quinones and aromatic amines is the formation of

substituted quinones. Typical examples are the reactions of quinones with primary aromatic

amines. Chloranil reacts with two equivalents of aniline to form 2,5-di-anilino-3,6-dichloro-p-

benzoquinone 2 through the EDA complexes10 (Scheme 2).

Aromatic amines react with TCNE more readily than the quinones. A substitution

reaction of tetracyanoethylene (TCNE), known as tricyanovinylation, is very facile even in

poor ionizing solvents. For example: in chloroform, TCNE reacts with dimethylaniline to give

4-tricyanovmyl-N,N-dimemylanilinea, 3 (Scheme 3). EDA complexation is also believed to

be the first step in this reaction.

103

NM^ O

6ofc DMA o

chloranil

.CI

*C1

EDA Complex ci^Y^c

n

.CI

'CI

JL CL DMA - ^ ^

-NMe.

D M A NMe, *"\ NMe2 T / / : = 5 * ( '

W O C M O r a n i l 'Me.H-C^X JT\S^ DMA M e ^ N " C > ^

i r JL ^ ^ ^

\=/ 2 OH

Cl^S^^Cl

""NMe,

\ H+

Me,

crystal) cation,

NMe,

NHMe

Scheme 1

104

O C K A ^ C 1 Ether/i-PrOH < ^ J L A

ci^Y^ci o

Scheme 2

NMe0 NMe0

NC CN CHCL rT^^i + > = < *~

NC CN

NC CN

Scheme 3

Chromophores and polymers for second-order nonlinear optics

Li recent years, nonlinear optical (NLO) polymers have become one of the most

exciting subjects in the area of organic materials.12,13 The linear and nonlinear optical behavior

of a material can be described by a series expansion of the polarization, P, in the material, in

powers of applied electric fields, E:

P = Po + X(1)E + 2C(2)EE + %(3)EEE +...

105

where Po is the permanent (or ground state) polarization, and %® are the susceptibilities. The

%(1) term describes ordinary linear behavior (refraction and absorption). The %C) and %0) are

the second-order and third-order nonlinear susceptibilities respectively. The same kind of

expression can be applied to a dipole moment, u., of an individual chromophore:

u. = Uo + aE + pEE + yEEE +...

where P is the second-order susceptibility tensor of the chromophore (also called the

quadratic hyperpolarizability, or first hyperpolarizability). Usually %c) is related to the P of the

chromophore from second harmonic generation (SHG) measurements in poled NLO films as

described in the following equation14.

%(2) = Np(02fJ<°<cos3e>

N is the number of chromophores per unit volume, f and f2m are the local field factors which

are simple functions of the index of refraction at fundamental and second harmonic

frequencies, and 0 is the average angle between the ground-state dipole moments of the

chromophores and the direction in the film they would be pointing if perfectly aligned, e.g.,

perpendicular to the plane of the polymer film.

The typical second-order NLO chromophores are organic donor-acceptor molecules.

A chromophore possessing a large p value is desirable. The P values of the chromophores are

generally increased with the molecular conjugated length and the strength of donors and

acceptors.15,16 The superiority of dicyanovinyl and tricyanovinyl groups to the nitro group in

enhancing the P values has been established.17 The synthesis of donor-acceptor 7c-conjugated

chromophores containing tricyanovinyl groups such as 4 and 5 was accomplished by the

tricyanovinylation of the corresponding thiophenes.18,19

106

There are four types of NLO polymers, guest-host systems, sidechain polymers,

mainchain polymers, and crosslinked polymers, known to date.14 Li the guest-host systems,

small unattached chromophores are dissolved in high molecular weight polymers. Generally a

guest-host system contains only about 10-30% by weight of the chromophore because the

higher levels tend to phase separate causing light scattering. A higher concentration of

chromophores can be achieved without causing inhomogeneity by incorporating the

chromophore into the polymers as in the sidechain, mainchain and closslinked polymers. The

sidechain polymers have one end of the chromophore chemically attached to the backbone

while the mainchain polymers have both ends of the chromophore linked in the backbone and

the chromophore becomes part of the polymer backbone. The crosslinked polymers are the

products from crosslinking of the guest-host systems, sidechain polymers or mainchain

polymers. Examples of these three types of NLO polymers are shown beow.

N02 CN CN

107

Mainchain Polymers21: *<K

NC

P JX, n

H H

Precursors for crosslinked polymers22 J > T v < l t {

L crosslinked by hv during poling crosslinked by heat

during poling

Li all types of NLO polymers, the chromophores need to be aligned, usually by electric

field poling, near the glass transition temperature.23 When the polymer is cooled and the field

is removed, the alignment can remain frozen. Li a crosslinked polymer, a precursor polymer

can be crosslinked during poling or after poling. The alignment stability is extremely

important for developing commercial devices from the NLO polymers. The stability is

generally in the order: guest-host system < sidechain polymers < mainchain polymers <

crosslinked polymers.14 Despite having the highest stability, the crosslinked polymers also

possess their own problem since they are more difficult to process and to control the quality.

108

RESULTS AND DISCUSSION

Reaction of electron-rich acetylene with TCNE

Electron donor-acceptor (EDA) complexes of acetylenic polymer 6 with organic

acceptors were studied by UV-Vis absorption spectroscopy. Four organic acceptors, iodine,

7,7,8,8-tetracyanoquino dimethane (TCNQ), 2,3-dichloro-5,6-dicyano-l,4-benzoquinone

(DDQ) and tetracyanoethylene (TCNE) were utilized in this experiment

N O X N

0 NCT^CN

TCNQ

NCX

0 *x II O

DDQ

NC CN

> = < NC CN

TCNE

A 1:1 mixture of polymer 6 with I2, TCNQ or DDQ in chloroform showed new

absorption bands at 612 nm, 651 nm and 710 nm respectively along with the modified

absorption band of polymer 6 around 375-400 nm (Figure 1). With TCNE, however, the

solution showed a very intense band at 512 nm with a disappearance of the absorption band of

the polymer. This result suggested that while I2, TCNQ and DDQ formed EDA complexes

with polymer 6, TCNE reacted with the polymer to form a new polymer.

109

300.0 550.0 800.0 Wavelength (nm.)

Figure 1 UV-Vis absorption spectra of a) polymer 6 and its 1:1 mixture with b) I2, c) TCNQ,

d) DDQ and e) TCNE in chloroform.

Another interesting feature of the absorption spectra is the absorption energies of the

new bands. The energies of these new absorptions of polymer 6 with the acceptors are 2.03

eV for I2,1.90 eV for TCNQ, 1.75 eV for DDQ and 2.42 eV for TCNE. The electron

affinities (EA) of the acceptors from the literature are 2.55 eV for h,2* 2.8 eV for TCNQ,24

3.12 eV for DDQ25 and 2.3 eV for TCNE.24 A plot of the absorption energies against the EA

of the corresponding acceptors is presented in Figure 2. A good linear relationship between

the EA and the absorption energies of the new bands was observed for the mixture of 6 with

I2, TCNQ and DDQ. The absorption energy of the mixture of TCNE and polymer 6 however

110

2.6 r

2.4-

2.2 2.15

EcT(eV) 2.0 -

1.8

1.6 -

0

XTCNE

DDQ

i i i i i i i i i

2.2 2.4 2.6 2.8 3.0 3.2 E A (eV)

Figure 2 Plot of the energy of the new observed absorption band against electron affinity (EA)

of the acceptors. The dashed line indicates the expected CT transition energy of the EDA

complex of TCNE with polymer 6.

deviated considerably from this linear relationship. With an EA of 2.3 eV, the expected CT

transition band of the EDA complex of TCNE with polymer 6 should be at 577 nm (2.15 eV).

Thus clearly a chemical reaction was involved in the mixture of TCNE and polymer 6.

An attempt to identify the product of the mixture of TCNE and polymer 6 by NMR

spectroscopy was performed. The XH-NMR of the mixture revealed only that the number of

proton resonances remained the same during the reaction. The 13C-NMR spectra was

complicated and more information was required to unambiguously characterize the product of

I l l

this mixture. However, it is very difficult to determine a structure of the polymer product

because some of the very useful characterization techniques, such as the mass spectrometry

and X-ray crystallography, are not applicable for polymers. Furthermore, if the reaction of

polymer 6 with TCNE was not quantitative, the resulting polymer would be a random

copolymer complicating its characterization. Thus a small model system was needed and a

simple anilinoacetylene, 4,4'-dimethylamino-diphenylacetylene 7, was synthesized.

1

Like polymer 6, a yellow solution of 7 in chloroform turned intensely red immediately after an

addition of one equivalent of TCNE. A UV-Vis absorption spectrum of acetylene 7 has bands

at 350 nm and 379 nm(Figure 3). Upon addition of TCNE, these absorption peaks

disappeared and only a new, intense peak at 468 nm was observed. This result agrees well

with the result obtained from the study of polymer 6 suggesting that model compound 7 and

polymer 6 underwent the same chemical reaction. XH-NMR and 13C-NMR spectra of 7 in

chloroform were recorded before and 10 minutes after the addition of TCNE. In the JH-NMR

spectra (Figure 4), the number of protons remained the same and all of the signals shifted

downfield upon equivalent addition of TCNE. In the 13C-NMR spectra (Figure 5), the

number of carbons increased by six and the acetylenic carbon signals disappeared. Thus the

reaction might be a [2 + 2] cycloaddition of the double bond of TCNE with the triple bond of

7. The exact mass obtained from electron impact (EI) high resolution mass spectrometry

112

1.000

A b s 0.500

0 .000 250.0 475.0

Wavelength (nm.) 700.0

Figure 3 UV-Vis absorption spectra of acetylene 7 in chloroform a) before and b) 10 minutes

after the addition of TCNE

(HIRES-MS) was equal to the sum mass of 7 with TCNE supporting a formation of a 1:1

adduct. The product from a [2 + 2] cycloaddition of TCNE to acetylene 7 would be a

cyclobutene adduct 8, but 13C-NMR shows no other sp3-C besides (iimethylamino groups.

However, the 13C-NMR spectra matched well with butadiene 9 which can be formed from an

electrocyclic ring opening of 8 (Scheme 4).26 A peak at 165 ppm is a dicyanovinylene carbon

peak which is very characteristic for this general structure.

113

II b II

l_L._i j.._ i — > — ' — ■ — ' — i — ■ — ■ — ' — ■ — i — ' — > - - >—>—i—■—*—■—■—i—■—■—■—■—i—■—■—■—■—i

-'—■—■—■—i—■—■—■—■—i—■—■—■—■—i—■—i—■—■—i—■—>-

7 .0 6.0 5.0 4 . 0 3 .0 ppm

Figure 4 'H-NMR spectra of acetylene 7 (a) before and (b) 10 minutes after the addition of

TCNE.

The structure of 9 was confirmed by X-ray crystallography. Single crystals of the

product was grown from a methanol/chloroform solution by allowing the solvents to slowly

evaporate. The deep red, shiny, metallic-like orthorhombic crystals were obtained from this

crystallization. The molecules of 9 in the crystal are not planar but twisted into an X shape

(Figure 6).

114

*+H*»it+mmy* *•*•** »»*f«*%»V»W^H<»Jftn»« WWorf *#•* wHt^^^ffh^prffh At «».>M Tf** -«»tV *»-Ww» f**«*" » »J ■* i*M w^*rt*ti* Lyw.^i ■■■»*»*** »w» *«*<*«» ■%—*■»*■ y^f»>««%^»MM<trww»

a -. I I . | i I I I | I I I ■ | I I I . ) i I I I | I i I I [ I i . I | i I I r ) I i i I | i I i . | i n I | i i I i | I i I i | i i i i ) i i I i ! i I i i | i i I i ! I i ■ I | i i i i | I i i ■ j i i i i | i i i i | i i i i ! i i i , | , i i i ! . , i i , i , ,

160 ISO 140 130 120 110 100 90 80 70 60 50 40

ppm

Figure 5 13C-NMR spectra of acetylene 7 (a) before and (b) 10 minutes after the addition of TCNE.

Me,N o~o NMe2

N C ^ C N

NC CN >-

CDC1, Me2N NMe2

I NC CN

NC-/ V- CN

Scheme 4

115

Figure 6 X-ray structure of 9

While a twisted structure is reasonable, resulting from the steric repulsions of four

substituents on two center carbons, (CI) and (CI'), the degree of twisting was quite

surprising. The dihedral angles between two anilinic groups (67.2°) and between two

malononitrile groups (63.5°), supposedly carrying the same partial charges, are about 50° less

than the dihedral angles between anilinic groups and malononitrile groups (113.2° and 116.1°)

which carry partial positive and negative charges respectively. The surprising small dihedral

angles between the same groups may be attributed to a strong intermolecular interaction

between anilinic groups and malononitrile groups of neighboring molecules in the crystal.

116

Because of the lack of a center of symmetry, this twisted structure is encouraging in the view

of using this unit for a second-order NLO chromophore. After an extensive literature search

we confirmed that compound 9 was not known but that the thermal [2+2] cycloadditions of

TCNE with alkenes and alkynes have been reported.

Generally, TCNE can form molecular EDA 7C-complexes with alkenes and alkynes

through the interaction of Tt-orbitals of the donors and acceptors. These it-complexes are

usually well behaved as the ionization energy values of the alkenes and alkynes are in good

agreement with the CT bands of the complexes.27,28 For some electron-rich alkenes and

alkynes, EDA complexation can eventually result in chemical reactions. A thermal [2 + 2]

cycloaddition between electron-rich alkenes with TCNE forming tetracyanocyclobutane was

first observed in 1962.29 The reaction generally occurs rapidly and in high yield at 0-30 °C.

The observation of highly colored solution at the beginning of the reaction indicated a

formation of a molecular EDA complex in the early step. For some cyclobutane adducts, a

ring cleavage with an elimination of HCN producing 1,1,2-tricyanobutadienes readily occur in

polar solvents such as alcohols (Scheme 5).30

NC CN / = + > = <

D NC CN

D . Q j L / ^ M e O ^ %

NC CN LJN

NC

H H

,CN XCN

o N -

Scheme 5

117

Formation of cyclobutenes from thermal [2 + 2] cycloadditions of electron-rich

alkenes and electron-deficient alkynes has been utilized as a synthetic tool in natural product

synthesis.31 The mechanistic work showed that 1,4-dipolar intermediates were formed before

the cyclization to form the cyclobutenes. The slow ring opening of the cyclobutene adducts to

form butadienes was also observed at room temperature. Scheme 6 shows the proposed

mechanism for an alkene containing an electron donor, D = OMe, and an alkyne containing

two electron acceptors, A = CC^Me, COPh, COMe.

D y = + A = A

D

Scheme 6

The thermal [2 + 2] cycloaddition between electron-rich acetylenes and TCNE has

only been reported for acetylene o-complexes of metals such as Pt, Ru or Fe (Scheme 7).32

The single electron transfer process was proposed to be involved before the formation of a

1,4-dipolar intermediate similar to that in the proposed mechanism in Scheme 6.

The reaction of TCNE with our acetylene 7 is formally a [2 + 2] cycloaddition

followed by electrocyclic ring opening to give tetracyanobutadiene (TCBD) 9. Presumably

this reaction is also initiated by electron transfer from acetylene 7 to TCNE to form radical

cation, 7**, and TCNE radical anion29,32 (Scheme 8). A nucleophilic attack of the radical anion

EDA Complex

118

NC CN

N C CN

(PPh3)2CIPt—^=—PtCl(PPh3)2

N C — « y>—CN

(PPh^CIPt' "PtCKPPh3)2 +

CN N C — ^ PtCl(PPh3)2

(PPh^CIp/ V-CN NC

Scheme 7

Me2N

NC^ ^CN

N C C N

M e ^ ■-0~~~0~*Sft4

NC CN •

N C C N

Me2N NMe2 Me2N NMe-

f\ /T\

NC-? f- CN NC CN NC

NC CN "CN NC CN

Scheme 8

on the triple bond of I** gives a 1,4-dipolar intermediate which closes to form cyclobutene.31

Electiocyclic ring opening of the unstable cyclobutene yields the final product, TCBD.

The synthesis of new chromophores with large P values and incorporating them into

polymer chains has been a very important part in the development of optimal second-order

119

NLO polymers for practical electro-optic devices.12,13,14 A high concentration of

chromophores in the polymer chain without any adverse effect on processibilities, optical

properties and mechanical properties of the polymers is highly desirable. Li polymer synthesis,

incorporating a high concentration of NLO chromophores into a polymer chain is quite a

synthetic challenge.

Two synthetic approaches to NLO polymers are: a) polymerization of monomers

containing NLO chromophores, and b) introduction of NLO chromophores into a polymer

chain by polymer modification. The TCNE reaction with electron-rich acetylenes fits into the

second approach and is particularly interesting because of a mild condition and excellent yield

of this reaction. The complete conversion of polymer 6 by the reaction with TCNE would

yield the interesting mainchain NLO polymer 10.

As mentioned in a previous section, the structural assignment for the product from the

mixture of polymer 6 and TCNE in chloroform was not possible from XH-NMR and 13C-NMR

spectra. The NMR spectra showed more proton and carbon peaks than expected from

complete reaction of 6, implying an incomplete conversion to polymer 10. Integration of XH-

NMR spectra indicated that only about 50 % of the acetylene units in polymer 6 were reacted.

This percent remained unchanged even after 48 hours.

120

A bigger acetylene, 11 resembling two repeating units of polymer 6 was thus

synthesized and used as a more representative model system. Acetylene 11 reacted slowly

with TCNE in chloroform and did not reach completion even after 24 hours. However, in

acetronitrile solution, a quantitative conversion of acetylene 11 to corresponding TCBD, 12,

was observed by XH-NMR within 10 minutes (Scheme 9). The faster reaction may largely be

due to a better solubility of TCNE in acetonitrile. The 1,4-dipolar intermediate is also

stabilized by the higher polarity of acetonitrile which should increase the rate of the reaction.

C 6 H 1 3

Me2N-HQ-^-HQ^N-^-^-HQH-NMe2

11

NC .CN 2 > = <

NC CN CD3CN quantitative

Me2N NMe„

Scheme 9

121

The reaction of TCNE with polymer 6 however cannot be performed in pure

acetronitrile due to the poor solubility of the polymer in this solvent. The reaction was thus

performed in a chloroform/ acetronitrile (70:30) mixed solvent In this mixed solvent, over .

95% conversion of acetylene units in polymer 6 to TCBD units in polymer 10 was obtained

within 24 hours as observed by JH-NMR (Figure 7). Less than 5% of unconverted acetylene

units can be observed in the *H-NMR spectrum of polymer 10 through the signals of aromatic

protons at 6-8-7.0 ppm and N-CH2 protons at 4.6-4.8 ppm. However, the 13C-NMR

spectrum (Figure 8) of polymer 10 is very clean indicating a virtually quantitative conversion.

JUL

Wo NC

NC-polymer.10 "CN

A_

JUl

C6H13

-N n o polymer 6

ppm

Figure 7 !H-NMR of polymer 6 and the product, polymer 10, from the reaction with TCNE.

122

C H NC Y6WI3

NC-polymer 10 CN

JL i

C6H13

polymer 6 o

J n

1 JULUL IM IM I4t 13f m H I

ppm

Figure 8 13C-NMR spectra of polymer 6 and the product, polymer 10, from the reaction with

TCNE.

On total conversion of polymer 6 to polymer .10, the molecular weight of the polymer

should be increased by 46% (compare the F.W. in Table 1). The GPC results showed that the

number average molecular weight of polymer 10 (2.22 x 104) was about 52% higher than that

of polymer 6 (1.46 x 104). This higher-than-theoretical value forMn maybe due to loss of the

lower molecular weight polymer during purification by precipitation of the product in

methanol. The loss of lower molecular weight polymer can also be observed through a slight

decrease (from 2.50 to 2.35) in polydispersity upon the conversion.

123

Table 1 Formula weight of a repeating unit (F.W.) and GPC results, number average

molecular weight (Mn), polydispersity (PD) and intrinsic viscosity (TJ), of polymers 6 and 10.

Polymer F.W. Mn Mw/Mn 11 (dL/g)

10

275.38 1.46 x 104

390.37 2.22 x 104

2.50

2.35

0.65

0.33

The concentration chromatograms of the polymers obtained from a tandem gel-

permeation chromatography-differential refractrometer (GPC-DR) (Figure 9) shows a very

similar molecular weight distribution of polymers 6 and 10. The reasonable increase of the

molecular weights of the polymers, and the similarities of the shape of the chromatograms

indicate that the addition reaction of TCNE to polymer 6 did not cause detectable chain

27 . e CONCENTRATION CHROMATOGRAM

Figure 9 GPC-DR concentration chromatograms of a) polymer 6 and b) polymer ,10.

124

fission or interchain crosslinking. It is worth noting that upon conversion of polymer 6 to

polymer 10 the intrinsic viscosity (T|) is decreased by half (Table 1), in spite of the increase in

molecular weight, indicating less rigidity in polymer chains of 10.

Thermal behaviors of polymer 10 were studied by thermogravimetric analysis (TGA)

and differential scanning calorimetric analysis (DSC) under nitrogen atmosphere. The TGA

showed the first weight loss at 314°C and 64% weight remaining from 600°C to 1000°C. The

second weight loss started at 1000°C and the weight dropped to zero after held for 60

minutes at 1100°C. The DSC showed no glass transition or melting point of the solvent free

polymer before crosslinking at 330°C. Li order to use this polymer as an NLO polymer, it will

need to be aligned at a glass transition temperature. This may require the presence of a small

amount of solvent or another polymer with a low glass transition temperature.

The expected product from the total conversion of diacetylene polymer ,13 with two

equivalents of TCNE was polymer ,14.

C 6 H 1 3

-•K>—O-2eq.

NC CN

NC CN

9&3

11

The XH-NMR and 13C-NMR spectra of the mixture of polymer 13 with two equivalents of

TCNE in CDCI3/CD3CN (70/30) was too complicated to assign a structure. Again, a study of

a small model compound was required. Diacetylene 15 was synthesized and used as a model.

The reaction of diacetylene 15 with excess TCNE gave a 1:1 adduct, 16 in quantitative yield.

125

It was hoped that increasing the reaction temperature would drive the reaction further to give

a 1:2 adduct, 17 (Scheme 10). It was also anticipated that at higher temperature 17 might

undergo an interesting electrocyclic ring-closure and retrocycloaddition to give 17-TCNE and

TCNE. The expected 1:2 adduct, 17, was however not observed and 16 remained unchanged

even when the reaction was conducted in refluxing dioxane. At higher temperatures, the 1:1

adduct, 16, started to decompose. The limited addition is conceivably caused by a steric

hindrance of the bulky tetracyano groups formed in the first addition.

Me^--o-^-o* NC CN

NC CN NC

NC CN

N C ^ T N CN NC

MejN

NMej

•NM^

Scheme 10

The addition of TCNE to the diacetylene polymer 13 was also likely limited to the 1:1

addition. In the polymer chain, there are two triple bonds for each repeating unit that TCNE

can react with. The random addition of TCNE to one of these two triple bonds generated a

regio-irregularity in the polymer which was observed by NMR. The NMR spectra consists of

many peaks which cannot be assigned to a single structure.

126

The adch^on/ring-opening reactions of TCNE with disubstituted electron-rich

acetylenes to form disubstituted TCBD electron donor-acceptor molecules is very facile, as

previously described. It was interesting to see whether monosubstituted electron-rich

acetylenes would undergo the same addition/ring-opening reaction, as the products would be

quite attractive since they should possess higher dipole moments and polarizabilities than their

disubstituted analogues. Therefore the reactions of TCNE with acetylenes 18 and 19 were

studied. Upon addition of one or two equivalents of TCNE to a solution of acetylene 18 or

acetylene .19 in acetonitrile, the color of the solution immediately became purple. ^-NMR

and 13C-NMR spectra identified the products as adducts from the addition/ring-opening

reactions. The conversion was facile at room temperature and generated the corresponding

mono and di-TCBD in quantitative yield (Scheme 11).

Me„N - O -NC CN

NC CN NC

CD3CN ->- Me2N

m

C 6 H 1 3

—OK) NC __ CN

NC CN ►NC

CD3CN

Scheme 11

127

Because the |3 values of chromophores generally increase with increasing lengths of n

conjugation21, this addition reaction of TCNE to a triple bond would be more valuable if it

could be applied to longer ir-conjugated acetylenes. An ethynyl derivative of aminostilbene 22

was synthesized and used as a substrate for the reaction with TCNE.

When one equivalent of TCNE was added to a solution of 22 in acetone-D6 , the color of the

mixture quickly changed from yellow to deep green. After 10 minutes the solution turned

light brown and eventually deep brown. This reaction was monitored by ^-NMR. During

the reaction of acetylene 22 with TCNE, new AB-quartet peaks centered at 5.4 ppm gradually

emerged at the expense of AB-quartet peaks centered at 7.2 ppm. This result unfortunately

corresponded to the formation of undesired tetracyanocyclobutane (TCCB) 23 from an

addition of TCNE to the double bond between two phenyl rings. When all the deep green

color disappeared, a quantitative conversion of 22 to TCCB 23 was observed by XH-NMR and

13C-NMR (Figure 10). The color of the solution slowly became dark brown as the product,

TCCB 23, decomposed (Scheme 12). XH-NMR signals corresponding to the desired product,

TCBD 24, were not observed during the course of the reaction. The decomposition products

could not be identified because the observed ^-NMR spectra became extremely complicated.

This result implied an inefficient delocalization of electron density from the amino group

through this 7t-conjugated system, thus the addition reaction at the triple bond was not

preferred.

128

lill 22

M JUL 23

' • 5 7 -° Ci 5-° 5 - 5 5"° «•' «■« 3-5 3.0 2is 2 ; 0 l is lio

hXJU-

22 ■Umfc»i ^*M^■ I»T ' * !>■! ■ ■lln»l l |M.l f c l i«< l i« J>N

23

fWV^j^Hj^'ftdhMMXf Aw*'1*

1**^^

Figure 10 *H-NMR and 13C-NMR of acetylene 22 and its adduct with TCNE,

tetracyanocyclobutane (TCCB) derivative 23.

129

Unidentified Products with Complicated NMR

NC Of NC CN

NC CN NC CN

21 - ^ ^ B . N NC

NC CN NC CN

Scheme 12

At this stage of our research a report on tricyanovinylations of extended Jt-conjugated

system (Scheme 13) appeared in Journal of Chemical Society, Chemistry Communication.18

The study showed that 4-diethylammostilbene was not reactive toward tricyanovinylation. By

replacing the designated benzene ring with thiophene, an electron-rich hetero cyclic, the

■-OA NC CN

NC CN

^ ^ C H ^ o NC>~V %N

Scheme 13

130

tricyanovinylation was accomplished. Using a similar concept, an ethynylthiophene %-

conjugated molecule, 25, was thus synthesized and used as a new substrate. A reaction of

TCNE with acetylene 25 in methylene chloride yielded a green solution containing exclusively

the desired TCBD product, 28. The reaction of acetylene 25 with TCNE was followed by JH-

NMR (Figure 11). The XH-NMR of the reaction of 25 with TCNE showed behavior similar to

the reaction of 22 with TCNE. New AB-quartet peaks centered at 4.9 ppm were observed

which correspond to the attack of TCNE at the central double bond of 25 to form TCCB 26.

The intensity of these AB-quartet peaks reached a maximum, then slowly decreased while a

singlet peak at 7.87 ppm started to appear with the corresponding reduction of the terminal

acetylene proton peak at 3.45 ppm, indicating the formation of the desired TCBD 28.

Eventually the AB-quartet peaks of TCCB 26 and the terminal acetylene proton peak

disappeared and only the new peaks of TCBD 28 was observed. Intermediates,

tetracyanocyclobutene 27 and 26+TCNE were also implicated by a couple of signals at 6.25

and 6.45 ppm, observed after 5 minutes, corresponding to protons on cyclobutene rings. The

reaction was completed within 10 minutes and TCBD 28 was the only observed product 13C-

NMR (Figure 12) confirmed the total conversion of acetylene 25 to TCBD 28. The transient

observation of intermediate 26 and 26+TCNE implies a reversibility of the addition of TCNE

(Scheme 14).

131

IJuJU before.

J UJL_ five minutes

- 1 1 1 1 ■ 1 1 1 1 1 1 . 1 | . r 1 , , , , , ■ , 1 ■ , 1 , ■ , 1 , 1 1 , , , 1 , 1 , , ,

7.S 7 .0 6.S 6.0 S.S S.O a . 5 4.0 3 .S

u ten minutes

1 T.I 7.« «.« ■ • S.S S.I I . I 4.1 3.1

ppm

Figure 11 IH-NMR of acetylene 25 before, five minutes and ten minutes after the addition of

TCNE.

132

VAV^w/'^ 'tY/WMVw u 25

'mj V^VVJVW v>Mj'^fY^M/v<^^i^^^

28

ppm

13, Figure 12 "C-NMR of acetylene 25 and its adduct with TCNE, tetracyanobutadiene (TCBD)

derivative 28.

The observation of TCCB 26 early but not at the end of the reaction indicates that

TCCB 26 is a kinetic product The final product, TCBD 28, should be a thermodynamic

product (Figure 13). For acetylene 22, the electron density on the triple bond is not high

enough to direct the attack of TCNE to yield the desired TCBD. 24. Only a kinetic product,

TCCB 23, was observed. By replacing the phenyl ring between the double bond and the triple

bond with an electron-rich heterocyclic thiophene ring, the activation energies of the addition

of TCNE on both double bond and triple bond are decreased. Acetylene 25 thus allowed an

attack of TCNE on the triple bond to form the thermodynamically stable TCBD 28 as a final

product

133

NC ▼ CN N C A - / - C N

Energy

Scheme 14

~2& \ 1 /

22 + TCNE or

21+ TCNE

\ cyclobutene intermediate

\ 4 \

2 2 \2A

reaction coordination

Figure 13 Energy diagram of the reaction of 22 and 25 with TCNE

134

Synthesis of dendrimers containing ethynylMphenylamine subunits was described in

part I of this thesis. The reaction of these dendrimers with TCNE would yield interesting

multipolar molecules which recently have attracted attention in the study of organic NLO

materials. Second order NLO properties of Multipolar chromophores such as crystal violet,

ruthenium tribipyridine complex (RuTB), and N,N'<Hethyl-4,6-dinitro-l,3-diaminobenzene

(DIEDD) were reported.33

Compared to their dipolar couterparts, these chromophores possess some favorable features:

(1) rounded shapes which allow single crystal packing, (2) lack of dipole moments, favoring

noncentrosymmetric crystal. (3) trigonal lamellar structures which increase electro-optic

modulator capacities, and (4) improved transparency and efficiency.

The reaction of GO dendrimer, 29, containing three triple bonds with three equivalents

of TCNE was performed in CD3CN and followed by XB and 13C-NMR. A yeUow solution of

29 turned deep red immediately after three equivalents of TCNE were added. XH and 13C-

NMR spectra showed that the reaction produced TCBD 30, in quantitative yield after 10

minutes. All of the three triple bonds were converted into TCBD units.

M^N NMe2

NMez

Me2N

NMe2

136

The Gl dendritic triphenylamine acetylene, 31, contains nine triple bonds. According

to XH and 13C-NMR, a reaction of dendrimer 31 with excess TCNE in CDCI3/CD3CN did not

give the product corresponding to the addition of all nine equivalents of TCNE. XH-NMR

spectrum (Figure 12) of Gl consists of three groups of greatly overlapped peaks from 6.5 to

7.4 ppm; a doublet at 6.5 ppm corresponding to the 12 outermost ortho (to dibutylamino)

protons, the overlapping peaks centered at 7.0 correspond to the 24 inner ortho (to nitrogen)

protons, and the peaks at 7.3 ppm correspond to the 36 meta (to nitrogen) protons. Upon the

reaction with TCNE, these three groups of peaks were separated and shifted downfield

137

indicating the addition of TCNE to some of the triple bonds. The 36 meta protons of Gl

were split into two groups containing 8 and 28 protons suggesting that an average of seven

acetylene units of each Gl molecule were converted to TCBD units (Figure 14). It however

remained uncertain whether the reaction produced a single product, or a mixture of products.

The 13C-NMR spectrum (Figure 15) appeared very complex and it was not possible to

assign all the signals. With careful and systematic analysis of this spectrum, a reasonable

structure for the product could be deduced. The single N-CH2 signal at 50.3 ppm indicates

full conversion of six outer triple bonds to six TCBD units. There are four possible products,

before

■ i i i i ■ ■ i ■ i ■ ■ i i i i i i ■ i i i ■ i i ■ ■ ■ ■ i ' ■ ■ ■ i i ■ ■ ' i ■ i ■ ■ i ' ■ ■ i i ' ■ ■ ■ i ■ ■ > ■ i ■ i ■ ■ i ■ ' ■ ■ i ■ 7 . 8 7 .7 7.6 7.S 7 .a 7 . 3 7 .2 7 . 1 7.0 6.9 6 . 8 6.7 6.6 6.S

after

1 ' ' I ' ' ' ' I ' ' ' ' I ' ■ ' ' I ' ' ■ ' I ' ' ' ' I ' ' ' ' I ■ ' ' ' I ■ ' ■ ' I ■ ' ' ' I ■ ' ' ■ I ■ ' ' ' I ' ' ' ' I ' ' ' ■ I ' 7 . 8 7 .7 7 .6 7.S 7 .A 7 . 3 7 .2 7 . 1 7.0 6.9 6 . 8 6.7 6.6 6.S

ppm

Figure 14 Aromatic *H-NMR spectra of Gl in CD3CN/ CDC13 before and thirty minutes after

the addition of 9 equvalents of TCNE.

138

1:6 adduct, 1:7 adduct, 1:8 adduct and 1:9 adduct, each having all of the outer acetylenes

converted (Figure 16). The spectrum shows six signals of sp2-C attached to N (a, b, c, d, e,f)

and six signals of sp2-C attached to malanonitrile group (a', V, c', d', e' f) which can be

expected from the 1:7 adduct and 1:8 adduct, but not from the 1:6 adduct or 1:9 adduct

which requires only 2 and 4 signals, respectively. The ratios of carbons for a:b:c:d:e:f and

a':b':c:'d':e':f are 4:4:1:1:2:2 and 2:2:2:2:4:4 for the 1:7 and 1:8 adducts, respectively. The

13C-NMR spectrum shows that the integration ratio of 4:4:1:1:2:2 matches with the 1:7

adduct. Thus, the product of the reaction of 31 with excess TCNE should be the 1:7 adduct,

31+7TCNE. exclusively. This deduction agrees with the integration of the lH-NMR spectum

and it is also reasonable based on the steric hindrance argument. The brief structure for 1:7

adduct (Figure 16) showed two seemingly equivalent unreacted diphenylacetylenes. a'.b' , a\b-

frVVV^ ti>^\tyhV-*»'**iwtyr>*h'F*A^

c, d

e,

w,

f x,x',y,y

165 160 155 I

150 — I —

145

*»fJ>W* yi wl U *wi\Jlt*w<0V*/Hmr<'l*0iJt' >pj VtfHuti^iiiwfr^VWWN^-fti 111 ■w«n*nAi»» >o»m»*^Uw\*M^\^J\n«n^f»n<iiiii

■Ul l I (TU |> l I T| I T l | | | H F j m T j I I I ) 11 I I I j I I I l | I I I I [ M I l | I I I I 11 H i i i i | i i i i | i n H n i i | i I I I | I M H I I I I | I I I i | r i i i | [ i i i | i i T i | i i i i | i M i | i i i i | i n 1111 i i | i> 111 r m ] i i i i j i 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 p p m

Figure 15 l3C-NMR spectra of the product of the reaction of Gl with TCNE.

139

BujN ^-N-^J^=-Q-N

-CN( a NC b

1:6 adduct

a CN ) NC

V i

BujN-:N,

NC" b

f CN NC-

N /

|l:7adduct|

NBuz

J 2 J 2

BuzN

NBu2

1:8 adduct

J 2

BiizN

Figure 16 Characteristic carbons of 1:6,1:7,1:8 and 1:9 adducts of Gl with TCNE.

140

However, the 13C-NMR showed four, instead of two, signals (x, x', y, y') of sp2-C attached to

N of these two unreacted diphenylacetylenes (insert in Figure 15). The full structure of

31+7TCNE showed that the molecule is chiral if the rotation about designated bond is

restrained (Figure 17). The four carbons (JC, X ' ; y, y') on these two diphenylacetylenes were

thus diastereotopic.

Figure 17 Structure of the 1:7 adduct showing two pairs of diastereotopic (x:x' and y:y')

carbons observed in 13C-NMR.

141

Ethynylbenzene was reported to form a molecular EDA complex with TCNE.27 Our

studies have shown that with an electron donor substituent such as an amino group on the

para position of ethynylbenzene, the triple bond reacts quickly with TCNE to form the TCBD

product in quantitative yields at ambient temperature. The monosubstituted electron-rich

acetylenes, both ethynylaniline 18 and diethynyldiphenyl-amine ,19 were described earlier as

reacting readily with one and two equivalents of TCNE, respectively, to form the

corresponding mono- and bis-TCBD in quantitative yield. The possible reaction of three

equivalents of TCNE with 4,4',4"-triethynyltriphenyl amine, 32, which contains three

acetylene groups and only one amino group was thus of interesting. The reaction was

conducted in CD3CN and studied by NMR. Remarkably, all three triple bonds of triacetylene

32 reacted readily with three equivalents of TCNE in acetonitrile to produce the

corresponding TCBD 33 in quantitative yield within 10 minutes (Scheme 15). This result was

not entirely expected considering that the additions of three molecules of TCNE to the triple

Scheme 15

142

bonds are stepwise, whereas the third equivalent of TCNE must add to the last triple bond of

the molecule already containing two strong electron withdrawing groups on the N of the

amino group. However, if each addition occurs before any of the cyclobutenes open it could

be argued that each addition step gets easier as N becomes more electron donating.

Another interesting and challenging substrate was cyanoacetylene 34, which contains a

strong electron withdrawing group (CN) on one extremity of the triple bond. This acetylene

presumably possesses a higher ionization energy than any other acetylenes which have been

used as substrates in our studies.

Bi^N—V J—^=—CN

The product from the addition/ring-opening reaction of TCNE with cyanoacetylene 34 would

be a novel pentacyanobutadiene (PCBD) which is interesting as a high P-value NLO

chromophore. Surprisingly, the reaction went rapidly in acetronitrile and a quantitative yield

of 35 (Scheme 16) was obtained within 10 minutes as observed by XH-NMR.

NC CN CD-CN 3J. + V = < —2-»» Btt N

NC CN

Scheme 16

143

So far, all of our studies have focused solely on the reaction of TCNE with aryl amines

containing ethynyl groups. This is because the alkoxy groups are poorer electron donors and

provide less diversity in structures as the oxygen is a divalent atom while the" nitrogen is a

tiivalent atom. However, it was of interest to see whether an electron-donating alkoxy group

would provide sufficient electron supply to produce the same reaction. Indeed, acetylene 36

was found to react with TCNE to give TCBD 37 in quantitative yield (Scheme 17).

NC CN

NC CN MeO—# ^ — = ► MeO -O—

2L CD3CN

Scheme 17

TCBD 37 can be crystallized from a toluene/chloroform solution to give red hexagonal

crystals. A big single crystal (3 mm x 5 mm x 1 mm) was obtained from this mixed solvent

The crystals, of TCBD 37 are transparent and glass-like, unlike the crystals of TCBD 20, the

amine analogue, or TCBD 35, which are shiny metal-like (Figure 18). Good transparency is

also one of the desired properties of the NLO chromophores for optical devices. This result

will provide more varieties of the monomer structures for designing new NLO polymers.

144

Me0N NMe„

NC

NC—^ 35 CN

MeO

Figure 18 Crystals of 20,37 and 35 shown 7 x actual sizes.

145

UV-Vis absorption spectra of the tetracyanobutadienes (TCBD)

Li order to be meaningful, NLO properties need to be studied in the region beyond the

electronic absorption bands to avoid the possible photochemical reactions and thermal effects

from the absorption.12 Therefore, the absorption characteristics of new NLO chromophores

need to be studied before the NLO properties. Furthermore, the absorption energies of the

chromophores provide information about the polarizabilities of the molecules as the

chromophores with higher polarizability usually absorb the light at lower energy (or longer

wavelength).12 In other words, molecules with lower electronic transition energies are more

polarizable. The UV-Vis absorption spectrum of each compound is also useful for

characterization, especially for a highly colored compound.

The UV-Vis spectra of all the new TCBDs were recorded and the absorption peaks

are presented in Table 2. The structure of the UV-Vis absorption spectra as well as the

position of the absorption peaks of disubstituted TCBDs (9, ,10, .12,30) are quite different

from monosubstituted TCBDs (20,21,33). The spectra of disubstituted TCBDs contained a

single broad absorption band in contrast to the spectra of monosubstituted TCBDs which

showed multiple absorption bands. The multiple bands observed in the monosubstituted

TCBDs still cannot be completely accounted for, but the availability of several conformations

in the monosubstituted TCBDs is a possible rationalization. The X^ of disubstituted TCBDs

are about 100 nm lower than the longest Xmax of monosubstituted TCBDs. The lower

absorption energies of monosubstituted TCBDs (2Q, 21 and 33), relative to the disubstituted

ones (9,12 and 30), suggest higher polarizabilities of the monosubstituted TCBDs.

146

Table 2 UV-Vis absorption peaks of the tetracyanobutadiene (TCBD) derivatives.

compound structure Amax

m

u

16.

Me2N

H13C6N

Me2N -O— NMe„

468

512

468

520

24 Me2N 346,571

147

Table 2 (Continued)

compound structure Amax

21

22.

H13C6N 303,355,590

314,450,656

2fi

22

2i

NMe,

J3

464

280,574

464

148

Table 2 (Continued)

compound structure Amax

2Z ' \ / \ 292,444

Due to the lower steric hindrance, the monosubstituted TCBD are more planar than the

disubstituted ones. The more planar structure allows better overlap of the 7t-orbitals and

better electron delocalization in the conjugated system resulting in lower band gaps between

the HOMO and LUMO.

The Amax of TCBD 9 (468 nm in chloroform) falls between the Amax of 4-dicyanovinyl-

N,N-dimethyaniline (420 nm in chloroform)17 and 4-ta^yanovmyl-N,N-dimethylaniline (521

nm in acetone)18 (Table 3). The longest A ax of TCBD 20 is the highest (571 nm in

chloroform). Comparison of these Amax suggests that the molecular polarizabilities of the

disubstituted TCBDs should be higher than the dicyanovinyl analogues and the molecular

polarizabilities of the monosubstituted TCBDs should be higher than the tricyanovinyl

analogues. The longest Amax of the new extended ^-conjugated TCBD 28 is 656 nm, which is

85 nm longer than the Amax of the simple TCBD 20. This considerable bathochromic shift

indicates that increasing the jc-conjugated lengths is indeed a good strategy to increase the

polarizabilities of these TCBD chromophores.

149

Table 3 Absorption peaks of the synthesized TCBD 9 and 20 compared to the known

dicyanovinyl and tricyanovinyl analogues.

compound Amax (nm)

Me2N

M e ^

42017 (chloroform)

52118 (acetone)

PCBD 35, containing five cyano groups on butadiene, was expected to absorb light at

longer wavelengths than the monosubstituted TCBD 20. The absorption spectrum of PCBD,

however, looks just like the absorption spectra of normal disubstituted TCBD, containing only

a single broad band with a Amax at 464 nm. This result suggests that the second substituent,

NC

NMe„ 468 (chloroform)

571 (chloroform)

Me2N

Me2N

150

even when it is an electron withdrawing group, on TCBD causes a negative effect on the Amax

and molecular polarizabilities of the chromophores.

Synthesis of the electron-rich acetylenes

Several reactions utilized in the synthesis of the electron-rich acetylenes in this Chapter

are the same as those of acetylene monomers in PART I, so they will be only briefly described

in this section. The ethynyl derivatives of anisole, N,N-dimethylaniline, N-hexyldiphenylamine

and triphenylamine (36,18,19,32) were synthesized from Heck-type coupling34 reactions of

appropriate iodo compounds with trimethylsilylacetylene followed by a base-catalyzed

desilyation35 (Scheme 18).

The iodo compounds 36-1 and 18-1 are commercially available but 19-1 and 32-1 were

synthesized from iodination of the N-hexyldiphenylamine* by a mild reagent, benzyltrimethyl-

ammonium dichloroiodate36 (Schemel9).

-SiMe,

r\ -I PdCl2(PPh3)2 r , _ , -, KOH I * ~ D - - ^ y—^=—SM^ J x Cul, DBU

Toluene Alcohol HO J x

21-1 ia-i ii-i 21-1

26-TMS 1S-TMS 12-TMS 21-TMS

2£D = MeO,x=l l £ D = Me2N,x=l 12D = H13C6N,x = 2 22D = N,x = 3

Scheme 18

* see page 69 for the synthesis and spectroscopic data of this compound.

151

HO J x

BTMAICL CaC03

CH2Q2

MeOH

r\ Jx

l£-IR = H13C6N,x = 2

21-ID=N,x = 3

Scheme 19

The disubstituted acetylenes 7, H and 29 were synthesized from the palladium

coupling34 reaction of 4-iodo-N,N-dimethylaniline with monosubstituted acetylenes 18,19 and

32, respectively (Scheme 20). The yields and spectroscopic data for these compounds are

presented in the experimental section.

Diacetylene ,15 was synthesized from an oxidative coupling37 of 4-ethynyl-N,N-

dimethylaniline 18 in 87% yield (Scheme 21).

IvfejN _£y.T + D-[(3-^ PdCL^Pl^ Cul, DBU

^-Toluene

ia-i lSD = Me2N,x=l I2D = H13C6N,x = 2 22D = N,x = 3

2D = Me2N,x=l I lD = H13C6N,x = 2 22D = N,x = 3

Scheme 20

Me„N -o is.

CuCl-TMEDA

02,THF (87%)

M e ^ -O- 4 \—NMe2

15.

Scheme 21

152

Synthesis of extended 7C-conjugated acetylene 22 is shown in Scheme 22. The Wittig

reagent precursor, 38,4-bromobenzylrriphenylphosphenium bromide, was obtained in

quantitative yield by refluxing a chloroform solution of triphenylphosphine and 4-

bromobenzylbromide.38,39 The Wittig reagent40,41 generated in situ from the precursor 38 by

sodium hydride in presence of 18-crown-6, reacted with 4-diehtylaminobenzaldehyde to give

4-diethylamino-4'-bromo-trans-stilbene, 22-Br, in 47% yield.

Br

BjN- r\ B r P h 3 P ,

f\ -Br

PPh3, CHC13 reflux (99%)

t

2S.

Br

NaH 18-crown-6

Ether, reflux (47%)

CuI(OAc)2-H20 PdCl2,PPh3,Et3N 85°C(65%)

!'2)KOH/i-PrOH(80%)

Scheme 22

The reaction also gave 30% of the cis-isomer as a byproduct. The palladium coupling42 of

bromostilbene 22-Br with trimethylsilylacetylene gave 4-d^ethylamino-4'-bromo-trans-stilbene,

22-TMS. The following base-catalyzed desilylation gave the desired acetylene 22 in 52%

yield (for the last two steps).

153

Another extended rc-conjugated acetylene containing a thiophene unit, 25, was

synthesized by the same sequences of reactions as for acetylene 22. A Wittig reaction of (5-

bromo-2-thenyl)triphenylphosphoniumbromide,43 39 with 4-diethylaminobenzaldehyde

produced 5-(4-N,N-diethylamino-P-trans-styryl)-2-bromo thiophene, 25-Br in 45%. The

subsequent palladium coupling of 25-Br with trimethylsilyl acetylene yielded 2-

trimethylsUylethynyl-5-(4-N,N-d^ethylamino-p-styryl) thiophene, 25-TMS, which was

subjected to a base-catalyzed desilylation to give 25.

The synthesis of the cyanoacetylene 34 was performed according to Scheme 23. Li a

one pot synthesis, 4-trimethylsUylethynyl-N,N-dibutylaniline* was treated with a solution of

methyllithium-lithium bromide complex.44 The reaction was then quenched by

phenylcyanate45 to give the desired product in 65% yield.

l)MeLi-LiBr/Ether THF -78°C - rt

Bu,N—f %—=—SiMe, ► BuJST—f ^ — ^ = — C N ^ \ = / 3 2)PhOCN \ = = /

-78°C-rt 21

Scheme 23

see page 87 for the synthesis of this compound.

154

EXPERIMENTAL

Characterizations of all synthesized compounds were based on exact mass, IR,

UV/Vis, XH-NMR and 13C-NMR.. The exact masses were obtained from a Kratos MS 50

mass spectrometer with 10,000 resolution. The infrared spectra were recorded on a Bio-Rad

Digilab FTS-7 spectrometer from neat samples. The UV/Vis spectra were acquired on a

Hewlett Packard 8452A diode array UV/Vis spectrometer and Amax were determined at optical

densities of 0.2-0.5. The XH and 13C NMR spectra were collected on a Varian VXR-300 MHz

spectrometer in deuterated chloroform solutions unless otherwise specified. Tentative signal

assignments of 13C-NMR spectra are given in parentheses after each chemical shift Reactions

were monitored by Hewlett Packard 5890 series IIGC and Hwelett Packard tandem GC-IR-

MS (5890A GC-5965AIR-5970 Series MS).

The thermal responses of polymers were studied on Du Pont Instruments 951

Thermogravimetric Analyzer (TGA) and 910 Differential Scanning Calorimeter (DSC) with a

scanning rate of 20°C/min for both analyses. Molecular weight distribution of polymers were

detemined by gel permeation chromatograph (GPC) system using universal calibration against

polystyrene standards (Mn = 2,000 -170,000). The GPC system consisted of a Beckman

HOB solvent delivery system, a Perkin-Elmer 601 liquid chromatograph equiped with six

Beckman 10 |X U-spherogel (7.7 mm x 30 cm) columns, a Viscotek 110 differential

viscometer and a Waters Associates R401 differential refractometer. The viscometer and

refractometer were parallel connected. The GPC analysis was performed at a flow rate of 1.0

mL/minofTHF.

155

THF was distilled over Na-benzophenone and ether was distilled over CaH2

immediately before use. Commercially available reagents were used as received unless

otherwise specified. Scientific Adsorbents 40 u. silica gel was utilized in flash

chromatography.

4-trimethylsiIylethynyl-N,N,-dimethylaniIine,18-TMS

A general procedure of palladium coupling of trimethylsilylacetylene with aryl iodide is

presented here. A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under

Ar, was charged with 4-iodo-N,N-dimethylaminobenzene (2.47 g, 10 mmol), PdCl2(PPh3)2(30

mg), Cul (19 mg) and DBU (1.64 g) and toluene (30 mL). Trimethylsilylacetylene (1.08g, 11

mmol) was added dropwise to this stirred solution. After 2 h the mixture was filtered and the

precipitate was washed with toluene (3 x 15 mL). The combined filtrate was concentrated

and the residue was eluted through a flash silica gel column by methylene chloride. The

solvent was removed and the resulting yellow solid was dried under vacuum for 24 h. to give

18-TMS (1.91 g, 88 %). IR (an1): 1515,2150,2806,2963; MS: 217 (M4), 202 (100%),

186,172,158,101.

4-ethynyI-N,N-dimethylaniline, .18

A general procedure of base-catalyzed desilylation is presented here. A 100 mL

round-bottomed flask equipped with a magnetic stirring bar, under Ar, was charged with 18-

TMS (1.5 g) and methanol (20 mL). Saturated KOH aqueous solution (0.2 mL) was added

dropwise to this stirred solution. After 6 h 10% potassium hydrogencarbonate solution (20

156

mL) and hexane (20 mL) was added to the mixture. The organic layer was separated and the

aqueous layer was extracted with hexane (2 x 20 mL). The combined organic layer was

washed with water (2 x 20 mL) and then dried over anhydrous MgS04. The solvent was

removed and the resulting yellow solid was dried under vacuum for 24 h. to give .18 (1.00 g,

95%). m.p.: 50-51 °C; HIRES EI: calcd for Ci0HnN 145.0892, measured 145.0891; UV

(CHCI3, nm): Amax = 292; IR (cm"1): 1516,1605,2814,2895,2097, 3266; XH-NMR

(CD3CN): 82.93 (6 H, s), 3.19 (H, s), 6.65 (2H, d/9.0), 7.30 (2H, d/9.0); 13C-NMR

(CD3CN): 8 40.2 (2 CH3), 76.2 (sp-CH), 85.3 (sp-C), 109.0 (sp2-C), 112.6 (2 sp2-CH),

133.7 (2 sp2-CH), 151.5 (sp2-C).

4,4'-diodo-N-hexyIdiphenylamine,!9-I

A general procedure for the iodination of arylamines by Benzyltrimethylammonium

chloroiodate36, BTMAICI2, is presented here. A 100 mL round-bottomed flask equipped with

a magnetic stirring bar, under Ar, was charged with N-hexyldiphenylamine (10.21 g, 40

mmol), methylene chloride (300 mL) and methanol (100 mL). BTMAIC12 (30.64 g, 88 mmol)

and CaC03 (11 g, O.llmol) were added quickly to this stirred solution. After 20 h, to the

mixture was added 20% NaHS03 solution until the mixture became colorless. The organic

layer was separated and the aqueous layer was extracted with methylene chloride (2 x 50 mL).

The combined organic layer was washed with water (2 x 100 mL) and dried over anhydrous

MgS04. The mixture was concentrated and the residue was eluted through a flash silica gel

column by hexane. The solvent was removed and the resulting yellow oil was dried under

vacuum at 65 °C for 24 h. to give 19-1 (4.40 g, 86%). HIRES EI: calcd for Ci8H2iNI2

157

504.9763, measured504.9694; 'H-NMR: 8 0.86 (3 H, t/7.0), 1.26 (6 H, m), 1.54 (2 H, qui

/7.0), 3.60 (2H, t/7.0), 6.73 (4H, d/9.0), 7.51 (4H, d/9.0); 13C-NMR: 8 14.0 (CH3),

22.6 (CH2), 26.6 (CH2), 27.1 (CH2), 31.5 (CH2), 52.2 (CH2), 83.9 (2 sp2-C), 129.0 (4 sp2-

CH), 138.1 (4 sp2-CH), 147.1 (2 sp2-C).

4,4'-bis(trimethyIsilyethynyl)-N-hexyIdiphenylamine,19-TMS

The palladium coupling of 19-1 and two equivalents of TMSA followed the procedure

in the synthesis of 18-TMS. Yield: quantitative (yellow oil); HIRES EI: calcd for

C28H39NSi2 445.2621, measured 445.2633; *H-NMR: 8 0.22 (18 H, s), 0.85 (3 H, t/7.0),

1.25 (6 H, m), 1.59 (2H, qui/7.0), 3.65 (2H, t/7.0), 6.87 (4H, d/9.0), 7.33 (4H, d /

9.0); 13C-NMR: 8 0.1 (3 CH3), 14.0 (CH3), 22.6 (CH2), 26.6 (CH2), 27.3 (CH2), 31.5 (CH2),

52.1 (CH2), 93.0 (2 sp-C), 105.4 (2 sp-C), 115.5 (2 sp2-C), 120.4 (4 sp2-CH), 133.1 (4 sp2-

CH), 147.4 (2 sp2-C).

4,4'-diethynyI-N-hexyldiphenylamine,!9

The base-catalyzed desilylation was performed in methanol/ f-propanol (1:2) using the

same procedure as in the synthesis of 18. Yield: 91% (yellow oil); HIRES EI: calcd for

C22H23N 301.1839, measured 301.1839,230.1 (100%); UV (CHC13, nm): Amax = 339,279;

IR(GC-IR, cm'1): 1504,2106,2938,3331; 'H-NMR (CD3CN): 8 0.87 (3 H, t/7.0), 1.28

(6 H, m), 1.63 (2 H, qui / 7.5), 3.02 (H, s), 3.68 (2 H, t / 7.5), 6.93 (4 H, d / 9.0), 7.38 (4 H,

d/9.0); 13C-NMR (CD3CN): 814.0 (CH3), 22.6 (CH2), 26.6 (CH2), 27.3 (CH2), 31.5

(CH2), 52.1 (CH2), 76.2 (2 sp-CH), 83.8 (2 sp-C), 114.5 (2 sp2-C), 120.5 (4 sp2-CH), 133.2

158

(4sp2-CH),147.6(2sp2-C).

4,4',4"-triiodotriphenylamine, 32-1

The triple iodination of triphenylamine was accomplished by using 3.3 equivalents of

the iodinating reagent, BTMAIC12. The reaction was performed at the reflux temperature of

mixed solvent of chloroform and methanol (2:1) for 36 h. The procedure and work up were

the same as in the synthesis of 19-1. Yield: 66%; 'H-NMR: 8 6.80 (6 H, d/9.0), 7.52 (6 H,

d/9.0), "C-NMR: 886.6 (3 sp2-C), 126.0 (6 sp2-CH), 138.4(6 sp2-CH), 146.5 (3 sp2-C).

4,4',4''-tris(trimethylsiIyIethynyl) triphenylamine, 32-TMS

The palladium coupling of 32-1 and three equivalents of TMSA followed the

procedure in the synthesis of 18-TMS. m.p.: 166-167 °C; HIRES EI: calcd for C33H39NSi3

533.2395, measured 533.2390; rR(cm'): 1502,1596,2155,2899,2958, 3038; 'H-NMR

(CD3CN): 80.23 (27 H, s), 6.94 (6 H, d/9.0),7.33 (6 H, d/9.0); 13C-NMR (CDC13): 8

0.0 (9 sp-CH3), 93.9 (3 sp-C), 104.8 (3 sp-C), 117.8 (3 sp2-C), 123.8 (6 sp2-CH), 133.1 (6

sp2-CH), 146.7 (3 sp2-C).

4,4',4"-triethynyltriphenylamine,32

The base-catalyzed desilylation was performed in methanol/ diethylether (1:1) with the

same procedure as in the synthesis of 18. Yield: 92%(yellow solid); m.p.: 108-110 °Q

HIRES EI: calcd for C24H15N 317.1209, measured 317.1204; IR(cm-'): 1598,2104, 3037,

3287; UV (CHCI3, nm): Amax = 282; 'H-NMR (CD3CN): 8 3.33 (3 H, s), 7.36 (6 H, d /

159

9.0), 6.96 (6 H, d/9.0); "C-NMR: 878.6 (3 sp-CH), 84.0 (3 sp-C), 117.6 (3 sp2-C), 125.0

(6 sp2-CH), 134.2 (6 sp2-CH), 148.0 (3 sp2-Q.

4,4'-dimethyIaminotoIan, 7

Acetylene 7 was obtained from a palladium coupling of 18 with 4-iodo-N,N-

dimethylaniline using the same procedure as in the synthesis of 18-TMS. Yield: 53 %; m.p.:

222-224 °C; HIRES EI: calcd for Ci8H2oN2 264.1665, measured 264.1631; UV (CHCI3,

nm): X^ = 332,352; IR(cm-'): 1527,1609,2807,2888; 'H-NMR: 8 2.96 (12 H, s), 6.64 (4

H, d/9.0), 7.37 (4H, d/9.0); 13C-NMR: 840.3 (4 CH3), 88.1 (2 sp-C), 111.1 (2 sp2-C),

111.9 (4 sp2-CH), 132.3 (4 sp2-CH), 149.7 (2 sp2-C).

bis-N,N-(4-dimethyIaminophenylethynylene-p-phenylene)hexylamine,H

Acetylene H was obtained from a palladium coupling of ,19 with two equivalents of 4-

iodo-N,N-dimethylaniline using the same procedure as in the synthesis of 18-TMS. Yield:

78%; m.p.: 146-147 °C; HIRES EI: calcd for C38H4iN3 539.330, measured 5539.3299; UV

(CHC13, nm): Amax = 332,360; IR(neat, cm1): 1506,1523,1609,2207,2803,2856,2926,

2951; 'H-NMR (CD3CN): 8 0.86 (3 H, t/7.0), 1.28 (6 H, m), 1.64 (2H, qui/7.0), 2.97

(12 H, s), 3.68 (2 H, t / 7.0), 6.64 (4 H, d / 9.0), 7.94 (4 H, d / 9.0), 7.38 (8 H, d / 9.0); 13C-

NMR (CD3CN): 8 14.0 (CH3), 22.6 (CH2), 26.7 (CH2), 27.4 (CH2), 31.6 (CH2), 40.2 (4

CH3), 52.2 (CH2), 87.4 (2 sp-C), 89.5 (2 sp-C), 110.5 (2 sp2-C), 111.8 (4 sp2-CH), 116.4 (2

sp2-C), 120.5 (4 sp2-CH), 132.3 (4 sp2-CH), 132.5 (4 sp2-CH), 146.8 (2 sp2-C), 149.8 (2 sp2-

C).

160

4,4',4"-Tris(4-dimethylaminophenyIethynyl) triphenylamine, 29

Acetylene 29 was obtained from a palladium coupling of 29-1 with three equivalents of

4-ethynyl-N,N-dmethylaniline using the synthesis procedure of 7. Yield: 83%; m.p.: 267°-

269 °C; DSC( rt-400 °C, rate 20 °C/min): HIRES EI: calcd for G B H ^ 674.34095,

measured 674.34140; m(crn'): 1501,1523,1609,2208,2803,2890,3037; UV (CHC13,

nm): Amax = 380; 'H-NMR (CD3CN): 8 2.98 (18 H, s), 6.66 (6 H, d / 9.0), 7.04 (6 H, d /

9.0), 7.40 (6 H, d/9.0), 7.41 (6 H, d/9.0); 13C-NMR (CD3CN): 840.1 (3 sp3-C), 87.2 (3

sp-C), 90.3 (3 sp-C), 110.1 (3 sp2-C), 111.8 (6 sp2-CH), 118.6 (3 sp2-Q, 123.8 (6 sp2-CH),

132.3 (6 sp2-CH), 132.5 (6 sp2-CH), 146.1 (3 sp2-Q, 149.9 (3 sp2-C).

bis-(4,4'-dimethyIaminophenyl) butadiyne, 15

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with CuCl (0.30g, 3.0 mmol) and THF (5 mL). Teframethylethylenediamine,

TMEDA, (0.20 mL, 1.3 mmol) was added to this stirred suspension. After 45 min the

mixture was allowed to settle, leaving a clear, deep blue-green solution of the CuCl-TMEDA

complex.

A three-necked 50 mL round-bottomed flask equipped with a magnetic stirring bar,

thermometer, cold-finger condenser and 0 2 inlet-outlet tubes, containing the solution of 4-

ethynyl-N,N-diinethylaniline, 18 (lg, 6.9 mmol) and THF (20 mL) was charged with a rapid

stream of 02. The solution was added dropwise with a CuCl-TMEDA complex solution (2

mL), freshly prepared as described above, and the temperature was maintained at 35-45 °C.

After 5 h the solution was filtered and the solid was washed several times with methylene

161

chloride until no more yellow filtrate obtained. The filtrate was combined and the solvent was

removed. The yellow residue was eluted through a flash silica gel column by methylene

chloride. The product was collected and the solvent was removed. Yield: 87 %; m.p.: 231

233 °C; HIRES EI: calcd for C20H20N2 288.1627, measured 288.1628; UV (CHC13, nm):

A ^ = 350,379; IR(cm-'): 1516,1601,2125,2143,2804,2921,2963; 'H-NMR (CD2C12): 8

2.97 (12H, s), 6.59 (4H, d/9.0), 7.37 (4H, d/9.0); 13C-NMR (CD2C12): 840.1 (4 CH3),

72.6 (2 sp-C), 82.3 (2 sp-C), 108.6 (sp2-Q, 111.6 (4 sp2-CH), 133.6 (4 sp2-CH), 150.3 (sp2-

C).

4-cyanoethynyI-N,N-dibutylaniIine, 34

A 100 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with 4-trimethylsUylethynyl-N,N-dibutylaniline (3.0 lg, 10 mmol) and dry THF (20

mL). The solution was cooled to-78°C. A solution ofMeLi'LiBr in diethylether (6.7 mLx

1.5 M, 10 mmol) was then added dropwise to this stirred solution.18 After 1 h the mixture

was allowed to warm to room temperature and maintained at this point for 8 h. The mixture

was again cooled to -78 °C. Phenyl cyanate19 ( 1.3 g, 11 mmol) was then added dropwise to

this mixture. The mixture was allowed to warm slowly to room temperature. After 8 h 6M

NaOH (40 mL) and ether (80 mL) was then added to the mixture. The organic layer was

extracted with 6M NaOH (3 x 40 mL), dried over MgS04 and the solvent was removed. The

residue was eluted through a flash silica gel column by hexane/ethylacetate (90:10). Further

purification by crystallization from hexane provided pure 24 (1.6 g, 63 %) as white crystalline

needles. m.p.: 61-62 °C; HIRES EI: calcd for Ci7H22N2 254.1780, measured 254.1785;

162

UV (CHC13, n m ) : U x = 348; IR(cm-'): 1598,2132,2224,2254,2870,2955; 'H-NMR

(CD3CN): 8 0.93 (6 H, t/7.5), 1.33 (4H, sex/7.5), 1.53 (4H, qui/7.5), 3.309 (4H, t /

7.5), 6.63 (2 H, d/21), 7.43 (2 H, d/21); "C-NMR (CD3CN): 814.1 (2 CH3), 20.7 (2

CH2), 29.7 (2 CH2), 51.1 (2 CH2-N), 62.2 (C6), 87.8(C5) 101.1 (C4), 107.3 (C7), 112.3

(C2), 136.1 (C3), 151.4 (CI).

4-bromobenzyItriphenylphosphinium bromide, 28

A 250 mL round-bottomed flask equipped with a reflux condenser, under Ar, was

charged with 4-bromobenzylbromide (5.00 g, 20 mmol) and chloroform (100 mL).

Triphenylphosphine (5.25 g, 20 mmol) was added to this stirred solution. After 72 h of reflux,

the mixture was allow to cool to room temperature and the solvent was removed. The residue

was precipitated in hexane from methylene chloride solution. After drying under vacuum at

65 °C for 24 h, 28 (10.1 g, 99%) was obtained as a white powder. 'H-NMR (DMSO-D6): 8

5.56 (2 H, d/15.0), 7.09 (2H, dd/8.5,2.5), 7.16 (H, d/8.5), 7.58-7.64 (6 H, m), 7.73-

7.81 (9 H, m); 13C-NMR (CDC13): 829.39 (CH2, d/186.0), 117.20 (3 sp2-C, d/340.0),

122.21 (sp2-C, d/19.0), 126.30 (sp2-C, d/34.0), 129.81 (6 sp2-CH, d/49.0), 131.33 (2

sp2-CH, d/11.0), 133.08 (2 sp2-CH, d/21.5), 134.16 (6 sp2-CH, d/38.5), 134.69 (3 sp2-

CH, broad).

4-diethylamino-4'-bromostiIbene, 22-Br

A 250 mL two-necked round-bottomed flask equipped with a magnetic stirring bar,

reflux condenser and additional funnel, under Ar, was charged with 4-bromobenzyltriphenyl

163

phosphenium bromide (18.96 g, 37 mmol) and dry ether (20 mL). A suspension of NaH (41

mmol), 4-N,N-diethylaminobenzaldehyde (4.37 g, 25 mmol) and 18-crown-6 (100 mg, 0.38

mmol) in ether (50 mL) was added dropwise to this stirred solution. After reflux for 8 h the

mixture was allowed to cool to room temperature and 3 M NH4CI solution (100 mL) was then

added. The aqueous layer was extracted with methylene chloride (2 x 50 mL) and the organic

layer was combined. The organic layer was washed with water (2 x 50 mL) and dried over

anhydrous MgS04. The solvent was removed. Precipitation of the residue in methanol from

methylene chloride solution yielded pure 22-Br (3.87 g, 47 %). m.p.: 149-150 °C; HIRES

EI: calcd for C18H20NBr 329.0779, measured 329.0788; IRCcm*1): 1520,2968,2887,2930;

'H-NMR: 8 1.20 (6 H, t/7.0), 3.39 (4H, q/7.0), 6.67 (2H, d/9.0), 6.81 (H, d/16.0),

7.03 (H, d/16), 7.33 (2H, d/8.5),7.39 (2H, d/9.0), 7.44 (2H, d/8.5); "C-NMR: 8

12.6 (2 CH3), 44.3 (2 CH2), 111.5 (2 sp2-CH), 119.8 (sp2-Q, 122.2 (sp2-CH), 124.1 (sp2-C),

127.3 (2 sp2-CH), 127.9 (2 sp2-CH), 129.6 (sp2-CH), 131.5 (2 sp2-CH), 137.2 (sp2-C), 147.5

(sp2-C).

4-diethyIanuno-4'-trimethyIsiIyIethynyI stilbene, 22-TMS

A 250 mL round-bottomed flask, equipped with a magnetic stirring bar and reflux

condenser, was charged with 4-diethylamino-4'-bromostilbene (3.30 g, 10 mmol), PdCl2 (177

mg, 1.0 mmol), Cu(OAc)2'H20 (200 mg, 1.0 mmol), triphenylphosphine (0.86 g, 3.3 mmol)

and degassed triethylarnine (100 mL). Trimethylsilylacetylene (1.47 g, 15 mmol) was added

dropwise to this stirred solution. The mixture was warmed to 85 °C. After 1 h the mixture

was allowed to cool to room temperature and then filtered. The filtrate was evaporated and

164

the residue was redissolved in methylene chloride (200 mL). The resulting solution was

filtered again and the solvent was removed. The residue was eluted through a flash silica gel

column by hexane/methylene chloride (80/20). The bright yellow solution was collected and

the solvent was removed. The product was dried under vacuum to give 22-TMS (2.25 g, 65

%) as a bright yellow powder. m.p.: 140-141 °C; HIRES EI: calcd for C2SH29NS1347.2069,

measured 347.2070; IR (cm"'): 1521,1592,1606,2152,2897,2966; 'H-NMR: 8 0.28 (9 H,

s), 1.18 (6 H, t/7.0), 3.38 (4H, q/7.0), 6.65 (2H, d/9.0), 6.84 (H, d/16), 7.05 (H, d /

16), 7.40 (6 H, m); 13C-NMR: 8 0.02 (3 CH3), 12.6 (2 CH3), 44.3 (2 CH2), 94.3 (sp-C),

105.6 (sp-C), 111.5 (2 sp2-CH) 120.6 (sp2-Q, 122.7 (sp2-CH), 124.2 (sp2-C), 125.6 (2 sp2-

CH), 128.0 (2 sp2-CH), 129.9 (sp2-CH), 132.1 (2 sp2-CH), 138.5 (sp2-C), 147.5 (sp2-C).

4-diethylamino-4'-ethynylstiIbene,22

The base-catalyzed desilylation of 24 in methanol/ THF (2:3) gave 18 in 80 %Yield;

m.p.: 128°-129 °C; HIRES EI: calcd for C20H2iN 275.1674, measured 275.1678; IR (cm"'):

1521,1594,1606,2098,2892,2974, 3280; 'H-NMR (acetone-D6): 8 1.14 (6 H, t/7.0),

3.41 (4H, q/7.0), 3.65 (H, s), 6.69 (2 H, d/9.0), 6.94 (H, d/16.5),), 7.17 (2 H, d/16.5),

7.41 (2 H, d / 9.0), 7.42 (2 H, d / 8.5), 7.51 (2 H, d / 8.5); 13C-NMR (acetone-D6): 8 12.9

(2 CH3), 44.8 (2 CH2), 79.3 (sp-CH), 84.5 (sp-C), 112.4 (2 sp2-CH), 120.7 (sp2-C), 122.9

(sp2-CH), 125.0 (sp2-C), 126.6 (2 sp2-CH), 128.9 (2 sp2-CH), 131.2 (sp2-CH), 133.0 (2 sp2-

CH), 140.0 (sp2-C), 148.6 (sp2-C).

165

(5-bromo-2-thenyl)triphenylphospheniumbromide,22

A 250 mL round-bottomed flask equipped with a magnetic stirring bar and reflux

condenser, under Ar, was charged with NBS (16 g, 90 mmol), benzoylperoxide (12 mg, 0.05

mmol) and carbon tetrachloride (60 mL). 2-Methylthiophene (4 g, 41 mmol) was then added

quickly to this solution at 100 °C. After 8 h another portion of NBS (2 g, 11 mmol) and

carbon tetrachloride (10 mL) was added to the mixture. After refluxing for 2 additional hours

the mixture was allowed to cool to room temperature. Hexane (50 mL) was added to the

mixture. The mixture was filtered and the filtrate was evaporated. The residue was

redissolved in chloroform (25 mL)/ hexane (25 mL). A solution of triphenylphosphine (10 g,

38 mmol) in 1:1 chloroform/ hexane (50mL) was then added to the solution while swirling.

The mixture was kept for 10 h in the open air and then hexane (100 mL) was added. The

mixture was then filtered and the precipitate was washed with cold acetone until the yellow

color disappeared. The off-white powder was dried under vacuum to give the desired product

(10.5 g, 50 %). m.p.: 261-263 (Lit 271-273 °C); 'H-NMR (DMSO-D6): 8 5.69 (2 H, d /

15.0), 6.69 (H, dd/4.0,3.5), 7.07 (H, dd/4.0, 0.5), 7.76 (12 H, m), 7.91 (3 H, m); 13C-

NMR (DMSO-D6): 824.44 (CH2, d/198.5), 112.26 (sp2-C, d/21.5), 117.50 (3 sp2-C, d /

342.0), 130.22 (6 sp2-CH, d/49.0), 130.47 (sp2-CH, d/13.0), 130.62 (sp2-CH, d/40.5),

131.53 (sp2-C, d/33.5), 133.94 (6 sp2-CH, d/40.0), 135.30 (3 sp2-CH, d /10.5).

2-bromo-5-(4-N,N-diethylamino-p-styryl)thiophene, 25-Br

A 250 mL round-bottomed flask equipped with a magnetic stirring bar and reflux

condenser, under Ar, was charged with (5-bromo-2-thenyl)triphenylphospheniumbromide

166

(13.5 g, 26 mmol) and dry ether (20 mL). A suspension of NaH (36 mmol), 4-N,N-

diethylaminobenzaldehyde (3.54 g, 20 mmol) and 18-crown-6 (80 mg, 0.3 mmol) in ether (40

mL) was added to this stirred solution. The mixture was refluxed for 8 h. The mixture was

allowed to cool to room temperature and 3 M NH4CI solution (100 mL) was then added. The

aqueous layer was extracted with methylene chloride (2 x 30 mL) and the organic layer was

combined. The organic layer was washed with water (2 x 50 mL) and dried over anhydrous

MgS04. The solvent was removed and the residue was redissolved in hot hexane. The

solution was filtered and the filtrate was evaporated. Precipitation of the residue in methanol

from methylene chloride solution yielded a crude product (~ 85% pure). The crude product

was eluted through a flash silica gel column by hexane/methylene chloride (19:1 -^ 3:1).

Evaporation of the solvents gave 25-Br (3.0 g, 45% yield). m.p.: 105-107 °C; HIRES EI:

caldfor Ci6Hi8BrNS 335.0343, measured 335.0340; IR(cm-'): 1514,1527,1600,2869,

2968; 'H-NMR: 8 1.18 (6 H, t/7.0), 3.37 (4H, q/7.0), 6.64 (2H, d/9.0), 6.69 (H, d /

3.5), 6.74 (H, d/16), 6.88 (H, d/16), 6.90 (H, d/3.5), 7.31 (2 H, d/9.0); 13C-NMR: 8

12.6 (2 CH3), 44.3 (2 CH2), 109.1 (sp2-C), 111.5 (2 sp2-CH), 116.2 (sp2-CH), 123.7 (sp2-C),

124.3 (sp2-CH), 127.7 (2 sp2-CH), 129.2 (sp2-CH), 130.2 (sp2-CH), 145.8 (sp2-C), 147.5

(sp2-C).

2-trimethyIsilylethvnyl-5-(4-N,N-diethylamino-P-styryl) thiophene, 25-TMS

A 100 mL round-bottomed flask equipped with a magnetic stirring bar and reflux

condenser 2-bromo-5-(4-N,N-ch^thylammo-p-styryl)thiophene (2.5 g, 7.4 mmol), PdCl2 (131

mg, 0.74 mmol), Cu(OAc)2-H20 (148 mg, 0.74 mmol), triphenylphosphine (0.639 g, 2.4

167

mmol) and degassed triethylamine (75 mL). Trimethylsilylacetylene (1.1 g, 11.1 mmol) was

added dropwise to the stirred solution. The mixture was warmed to 85 °C. After 1 h the

mixture was allowed to cool to room temperature and then filtered. The filtrate was

evaporated and the residue was redissolved in methylene chloride (200 mL). The resulting

solution was filtered again and the solvent was removed. The residue was eluted through a

flash silica gel column by hexane/ methylene chloride (1:0 -> 4:1). The bright yellow solution

was collected and the solvent was removed. Further purification by precipitation in methanol

from methylene chloride solution yielded 25-TMS (1.0 g, 39 %) as a bright yellow powder.

m.p.: 122-124 °C; HIRES EI: calcd for C2iH27NSSi 353.1634, measured 353.1630; IR (cm

') : 1526,1601,2140,2869,2966; 'H-NMR: 8 0.23 (9 H, s), 1.16 (6 H, t /7.0), 3.36 (4 H, q

/7.0), 6.62 (2H, d/9.0), 6.77 (H, d/3.5), 6.80 (H, d/16), 6.90 (H, d/16), 7.07 (H, d /

3.5), 7.30 (2 H, d/9.0); 13C-NMR: 8 -0.1 (3 CH3), 12.6 (2 CH3), 44.4 (2 CH2), 98.3 (sp-C),

99.2 (sp-C), 111.6 (2 sp2-CH) 116.3 (sp2-CH), 119.8 (sp2-C), 123.7 (sp2-C), 124.0 (sp2-CH),

127.9 (2 sp2-CH), 129.9 (sp2-CH), 133.4 (sp2-CH), 146.0 (sp2-C), 147.6(sp2-C).

2-ethynyI-5-(4-N,N-diethyIamino-P-styryl) thiophene, 25

The base-catalyzed desilylation of 25-TMS in methanol/ THF (2:3) gave 25 in 80%

yield; m.p.: 99-100 °C; HIRES EI: Ci8H19NS 281.1238, measured 281.1236; UV (CHC13,

nm): Amax = 402; m(cm"'): 1513,1524,1599,2097,2871,2968, 3296; 'H-NMR: 8 1.17 (6

H, t/7.0), 3.38 (4 H, q/7.0), 3.45 (H, s), 6.65 (2H, d/9.0), 6.84 (H, d/3.5), 6.85 (H, d /

16), 6.95 (H, d/16), 7.15 (H, d/3.5), 7.32 (2 H, d/9.0); 13C-NMR: 812.7 (2 CH3), 44.7

(2 CH2), 77.8 (sp-C), 81.9 (sp-CH), 111.8 (2 sp2-CH), 116.1 (sp2-CH), 118.7 (sp2-C), 123.7

168

(sp2-C), 124.3 (sp2-CH), 128.2 (2 sp2-CH), 130.6 (sp2-CH), 134.2 (sp2-CH), 146.6 (sp2-C),

148.1 (sp2-Q.

4-ethynyIanisoIe, 26

Acetylene 36 was synthesized in two steps, palladium coupling with

trimethylsilylacetylene followed by base-catalyzed desilylation, from 4-iodoanisole. The

procedure of the synthesis is similar to the synthesis of 4-ethynyl-N,N-dimethylaniline. The

compound was characterized by only 'H and 13C-NMR. 'H-NMR (CD3CN): 8 3.27 (1 H, s),

3.88 (3 H, s), 6.88 (2 H, d/12.0), 7.41 (2 H, d/12.0), 8.20 (1 H, s); 13C-NMR (CD3CN): 8

56.0 (CH3), 77.4 (sp-CH), 84.2 (sp2-C), 114.8 (sp-C), 134.4 (2 sp2-CH), 161.0 (sp2-C).

Polymer ,10

A 25 mL round-bottomed flask equipped with a magnetic stirring bar, under Ar, was

charged with polymer 6 (200 mg, 0.73 mmol), chloroform (9 mL) and acetonitrile (3 mL).

Freshly sublimed TCNE (95 mg, 0.74 mmol) was added to this stirred solution. After 24 h

the mixture was added dropwise by a Pasteur pipette into 100 mL methanol. The red

precipitate was collected by filtration and reprecipitated in methanol from a methylene

chloride solution. The obtained polymer was dried under vacuum at 65 °C for 36 h to yield

pure 10 (236 mg, 80%) 'H-NMR: 8 0.86 (3 H, br.), 1.30 (6 H, br), 1.71 (2 H, br), 3.87 (2

H, br.), 7.20 (4H, d/8.5), 7.78 (4H, d/8.5); 13C-NMR : 8 13.8 (CH3), 22.4 (CH2),26.4

(CH2), 27.6 (CH2), 31.2 (CH2), 52.8 (CH2), 82.5 (2 sp2-C), 111.9 (2 CN), 112.7 (2 CN),

121.4 (4 sp2-CH), 124.9 (4 sp2-C) 131.8 (4 sp2-CH), 151.1 (2 sp2-C), 164.8 (2 sp2-C).

169

bis-cc,a'-(-4-dimethylamino-P,P-dicyanostyrene),9

A general procedure for the study of the reaction of TCNE with acetylene 9 and other

electron-rich acetylenes is described here. The reaction of TCNE with electron-rich

acetylenes was performed in a 5 mL NMR tube. 'H and 13C-NMR spectra of a solution of

acetylene 9 (30 mg) in deuterated chloroform were recorded. An equivalent of freshly

sublimed TCNE was added to this solution, and the mixture was intermittently agitated. The

solution was deep red. After 10 min the 'H and 13C-NMR spectra of the of the mixture were

recorded again. Percent conversion and yields were determined by ^-NMR. The metallic

shiny crystalline product were obtained from crystallization of the product in

chloroform/methanol. Yield: quantitative; m.p.: 268-270 °C; HIRES EI: calcd for C^oNe

392.1749, measured 392.1746; 184.1 (100%); UV (CHC13, nm): Amax = 468; mfcm"1): 1605,

2135,2216,2929; 'H-NMR: 8 3.12 (12 H, s), 6.67 (4 H, d / 9.5), 7.77 (4 H, d / 9.5); 13C-

NMR: 8 40.0 (4 CH3), 74.5 (2 sp2-Q, 111.9 (4 sp2-CH), 113.5 (2 CN), 114.7 (2 CN), 118.7

(2 sp2-C), 132.5 (4 sp2-CH), 154.1 (2 sp2-C), 165.4 (2 sp2-C).

12

The reaction of H with two equivalents of TCNE was performed in deuterated

acetonitrile using the same procedure as in the synthesis of 2- The solution was deep red.

Evaporation of the solvent gave black powder of 12. Yield: quantitative; m.p.: 165-167 °C;

EI: C50H41N11 795.3,169.8 (100%); UV-(CHCI3, nm): X^ = 268,468; IR(cm-'): 1589,

1606,2217,2859,2929; 'H-NMR (CD3CN): 8 0.86 (3 H, t/7.0), 1.29 (6 H, m), 1.63 (2 H,

qui/7.0), 3.15 (12H, s), 3.82 (2H, t/7.0), 6.72 (4H, d/9.0), 7.13 (4H, d/9.0), 7.74 (4

170

H, d/9.0), 7.78 (4H, d/9.0); 13C-NMR (CD3CN): 8 13.9 (CH3), 22.5 (CH2), 26.5 (CH2),

27.6 (CH2), 31.3 (CH2), 40.2 (4 CH3), 52.6 (CH2), 73.8 (2 sp2-Q, 82.3 (2 sp2-C), 112.0 (2

CN), 112.2 (4 sp2-CH), 113.0 (2 CN), 113.5 (2 CN), 114.4 (2 CN), 118.0 (2 sp2-C), 121.2 (4

sp2-CH), 125.5 (2 sp2-Q, 131.8 (4 sp2-CH), 132.5 (4 sp2-CH), 150.8 (2 sp2-Q, 154.4 (2 sp2-

C), 163.5 (2 sp2-Q, 166.7 (2 sp2-C).

3Q

The reaction of 29 with three equivalents of TCNE was performed in deuterated

acetonitrile using the same procedure as in the synthesis of 9. The solution was deep red.

Evaporation of the solvent gave black powder of 2Q. Yield: quantitative; m.p.: >300 °C;

IR(cm-'): 1536,1605,2216,2812,2921,3090; UV (CHCI3, nm): Amax = 464; 'H-NMR

(CD3CN): 83.16 (18 H, s), 6.73 (6 H, d/9.5),7.21 (6 H, d/9.5),7.72 (6 H, d/9.5),7.79

(6 H, d/9.5); 13C-NMR (CD3CN): 840 0 (6 CH3), 73.0 (3 sp2-Q, 84.9 (3 sp2-C), 111.5 (3

CN), 112.2 (6 sp2-CH), 113.6 (3 CN), 114.2 (3 CN), 117.3 (3 CN), 124.8 (6 sp2-CH), 127.8

(3 sp2-C), 131.5 (6 sp2-CH), 132.3 (6 sp2-CH), 149.5 (3 sp2-C), 154.4 (3 sp2-C), 162.5 (3 sp2-

C), 166.8 (3 sp2-C).

2-(p-dimethyaminophenyl)-l,l,4,4-tetracyanobutadiene, 20

The reaction of 18 with an equivalent of TCNE was performed in deuterated

acetonitrile using the same procedure as in the synthesis of 9. The solution was deep blue

Evaporation of the solvent gave black powder of 20. Yield: quantitative; m.p.: 152-153 °C;

HIRES EI: calcd for QeHnNs 273.1014, measured 273.1014; UV (CHC13, nm): Amax = 270,

171

343,571; IR(cm-'): 1537,1604,2216,2317,2923,3031; 'H-NMR (CD3CN): 8 3.10 (6 H,

s), 6.80 (2H, d/9.0), 7.59 (2H, d/9.0), 8.25 (H, s); 13C-NMR (CD3CN): 840.3 (2 CH3),

78.0 (sp2-Q, 97.5 (sp2-Q, 110.7 (CN), 112.6 (2 sp2-CH), 112.8 (CN), 114.4 (CN), 115.3

(CN), 118.5 (sp2-Q, 133.2 (2 sp2-CH), 155.3 (sp2-Q, 158.9 (sp2-C), 160.8 (sp2-Q.

4,4'-bis(l,l,4,4-Tetracyanobutadien-2-yl)-N-hexyIdiphenylamine,21

The reaction of 21 with two equivalents of TCNE was performed in deuterated

acetonitrile using the same procedure as in the synthesis of 9. The solution was deep blue.

Evaporation of the solvent gave black powder of 21. Yield: quantitative; m.p.: 184-186 °C;

HIRES EI: calcd for C34H23N9 557.2076, measured 557.2066; base peak 486.1; UV (CHCI3,

nm): Amax = 303,355,590; IR (cm'1): 1588,1609,1750,2223,2859,2930,2957,3036; 'H-

NMR (CD3CN): 8 0.85 (3 H, t/7.0), 1.27 (6 H, m), 1.66 (2H, qui/7.0), 3.87 (2 H, t /

7.0), 7.23 (4 H, d/9.0), 7.55 (4H, d/9.0), 8.22 (H, s); 13C-NMR (CD3CN): 814.2 (CH3),

23.2 (CH2), 27.0 (CH2), 27.9 (CH2), 32.1 (CH2), 53.2 (CH2), 88.4 (2 sp2-C), 98.0 (2 sp2-C),

110.5 (2 CN), 112.8 (2 CN), 113.2 (2 CN), 113.8 (2 CN), 122.4 (4 sp2-CH), 125.4 (2 sp2-C),

132.7 (4 sp2-CH), 152.0 (2 sp2-CH), 156.0 (2 sp2-C), 162.1 (2 sp2-C).

4,4',4''-tris(l,l,4,4-tetracyanobutadien-2-yl)triphenyIamine,22

The reaction of 21 with three equivalents of TCNE was performed in deuterated

acetonitrile using the same procedure as in the synthesis of 9. The solution was deep blue.

Evaporation of the solvent gave black powder of 22. Yield: quantitative; m.p.: > 300 °C

(soften at 140°C); HIRES EI: calcd for C42Hi5Ni3 701.1573, measured 701.1576; IR (cm"'):

172

1588,1749,2226,3035; UV (CHCI3, nm): complex structure around 250-400 and a broad

peak at 574; 'H-NMR (CD3CN): 8 7.30 (6 H, d / 9.0), 7.52 (6 H, d / 9.0), 8.21 (3 H, s);

13C-NMR (CD3CN): 8 91.8 (3 sp2-Q, 98.2 (3 sp2-Q, 110.4 (3 CN), 112.2 (3 CN), 113.2 (3

CN), 118.3 (3 CN), 126.1 (6 sp2-CH), 127.7 (3 sp2-Q, 132.5 (6 sp2-CH), 151.0 (3 sp2-CH),

154.9 (3 sp2-C), 162.3 (3 sp2-Q.

l,l-dicyano-2-(p-dimethylamino-p,P-dicyanostyryl)-4-(p-dimethylaminophenyl)but-l-

en-3-yne, 16

The reaction of 15 with two equivalents of TCNE was performed in deuterated

methylene chloride using the same procedure as in the synthesis of 9. The solution was deep

red. Evaporation ofthe solvent gave black powder of 16. Yield: quantitative; m.p.: 192°-

194 °C; UV (CHC13, nm) : Amax = 520; IRCcm"1): 1538,1602,2133,2216,2811,2917,3083;

HIRES EI: calcd for C26H2oN6 416.1749, measured 416.1746; 'H-NMR (CD2CI2): 8 3.09 (6

H, s), 3.15 (6 H, s), 6.68 (2 H, d / 9.0), 6.76 (2 H, d / 9.0), 7.49 (4 H, d / 9.5), 7.82 (4 H, d /

9.5); 13C-NMR (CD2C12): 840.2 (2 CH3), 40.3 (2 CH3), 74.1 (sp2-C), 87.8 (sp-C), 90.5 (sp-

C), 105.1 (sp2-C), 112.0 (CN), 112.1 (4 sp2-CH), 113.0 (CN), 113.9 (CN), 115.0 (CN), 117.8

(sp2-C), 125.6 (sp2-C), 132.8 (2 sp2-CH), 136.2 (2 sp2-CH), 150.2 (sp2-C), 153.5 (sp2-C),

154.8 (sp2-C), 161.6 (sp2-C).

23

The reaction of 22 with an equivalent of TCNE was performed in deuterated acetone

using the same procedure as in the synthesis of 9. The solution was light brown. The product

173

decomposed slowly and no isolation was attempted. Yield: quantitative ('H-NMR); 'H-

NMR (acetone-D6): 8 1.12 (6 H, t/7.0), 3.40 (4H, q/7.0), 3.76 (H, s), 5.27 (H, d /

13.0), 5.47 (H, d /13.0), 6.76 (2 H, d / 9.0), 7.54 (2 H, d / 9.0),), 7.62 (2 H, d / 8.5), 7.69

(2H, d/8.5); 13C-NMR (acetone-D6): 812.3 (2 CH3),41.7 (sp3-C),43.3 (sp3-C), 44.3 (2

CH2), 51.1 (sp3-CH), 51.8 (sp3-CH), 80.5 (sp-CH), 82.8 (sp-C), 110.3 (CN), 110.5 (CN),

111.5 (CN), 111.6 (CN), 111.9 (2 sp2-CH), 117.1 (sp2-C), 124.4 (sp2-C), 128.7 (2 sp2-CH),

129.9 (2 sp2-CH), 133.1 (2 sp2-CH), 133.3 (sp2-C), 149.5 (sp2-C).

28

The reaction of 25 with an equivalent of TCNE was performed in deuterated

acetonitrile using the same procedure as in the synthesis of 9. The solution was deep puple.

Evaporation of the solvent gave black powder of 28. Yield: quantitative ('H-NMR); m.p.:

179-181 °C; HIRES EI: calcd for C24H19N5S 409.1361, measured 409.1357; UV (CHC13,

nm): Amax = 656,450,314; IR (crn'): 1511,1585,2214,2972; 'H-NMR (CD2C12): 81.20

(6 H, t/7.0), 3.43 (4H, q/7.0), 6.68 (2H, d/9.0), 7.01 (H, d/16.0), 7.17 (H, d/4.5),),

7.22 (2H, d/16.0), 7.41 (2H, d/9.0), 7.57 (H, d/4.5),7.87 (H, s); 13C-NMR (CD2C12):

8 12.7 (2 CH3), 44.9 (2 CH2), 74.3 (sp2-C), 97.4 (sp2-C), 109.6(CN), 111.2 (CN), 111.9 (2

sp2-CH), 113.5 (CN), 114.0 (CN), 114.4 (sp2-CH), 122.6 (sp2-C), 126.7 (sp2-CH), 129.7

(sp2-C), 130.1 (2 sp2-CH), 137.9 (sp2-CH)* 139.3 (sp2-CH), 149.7 (sp2-Q, 150.0 (sp2-C),

155.7 (sp2-CH), 159.7 (sp2-C).

174

4-(l,l,2,4,4-pentacyanobutadien-3-yl)-N,N-dibutyIaniline,25

The reaction of 24 with an equivalent of TCNE was performed in deuterated

acetonitrile using the same procedure as in the synthesis of 9. The solution was deep puple.

Crystallization of product from methylene chloride/hexane gave shiny deep violet crystals of

25. Yield: quantitative; m.p.: 103-105 °C; HIRES EI: calcd for C23H22N6 382.1906,

measured 382.1906; UV (CHC13, nm): Amax = 464; IR (neat, cm*'): 1604,2215,2873,

2933,2961; 'H-NMR (CD3CN): 8 0.94 (6 H, t/7.5), 1.36 (4H, sex/7.5), 1.59 (4 H, qui/

7.5), 3.46 (4H, t/7.5), 6.84 (2H, d/9.5), 7.70 (2H, d/9.5); 13C-NMR (CD3CN): 8 14.0

(2 CH3), 20.6 (2 CH2), 29.9 (2 CH2), 51.7 (2 CH2), 74.2 (sp2-C), 107.9 (CN), 109.5 (CN),

110.9 (CN), 112.7 (CN), 113.6(2 sp2-CH), 114.5 (sp2-C), 115.4 (CN) 117.4 (sp2-C), 134.1 (2

sp2-CH), 139.8 (sp2-C), 153.8 (sp2-C) 154.9 (sp2-Q.

4-(l,l,4,4-tetracyanobutadien-2yl) anisole, 22

The reaction of 26 with an equivalent of TCNE was performed in deuterated

acetonitrile using the same procedure as in the synthesis of 9. The solution was transparent

redish-orange. Crystallization of product from methylene chloride/hexane gave transparent

red crystals of 22. Yield: quantitative ('H-NMR); m.p.: HIRES EI: calcd for C15H9N4O

(M+H) 261.0778, measured 261.0776; UV (CHC13, nm): 292,444; IR (neat, cm1):; 'H-

NMR (CD3CN): 8 3.88 (3 H, s), 7.11 (2 H, d/9.0), 7.54 (2 H, d/9.0), 8.20 (i H, s); 13C-

NMR: 855.8 (CH3), 98.1 (sp2-C), 108.5 (CN), 111.2 (CN), 111.6 (CN), 111.8 (CN), 115.7

(sp2-CH), 122.3 (sp2-C), 131.4 (2 sp2-CH), 153.4 (sp2-CH), 161.4 (sp2-C) 164.6 (sp2-C).

175

CONCLUSIONS

Li the first part, the syntheses of linear and dendritic polymers containing hole

transporting units, di- and triphenylamine, were accomplished by Pd-coupling polymerization

and oxidative coupling. High molecular weight polymers were obtained in the presence of a

strong base such as DBU. Spectroscopic and electrical conductivity studies of these polymers

indicated that the electronic properties of these polymers depended mainly on the structure of

their individual repeating units. The benzene rings in the linear polymers are likely highly

twisted from the p-orbital of N and the polymer chains may develop helical secondary

structures prohibiting extensive conjugation. The introduction of N atom into conjugated

chain enhanced the solubilities and the flexibility of the polymers. Even though the

preliminary results of electroluminescence and conductivity studies have not showed

impressive numbers, the modification of conjugation segments by replacing ethynylene to

vinylene showed some positive results on the photoluminescence and conductivity.

Li the second part, the synthesis of new electron donor-acceptor tetracyanobutadienyl

(TCBD) derivatives from a facile thermal cycloaddition-ring opening reaction of TCNE on

electron-rich aromatic acetylenes were studied. A very efficient conversion of the substrate to

TCBD was found in monosubstituted and disubstituted acetylenic anilines. This reaction

offers a new convenient and efficient synthetic route to new NLO chromophores and polymers

from acetylenic monomers and polymers. A new mainchain NLO polymer, polymer 10, was

the first example in this regard. Some disubstituted acetylenes with bulky substituents in this

study have showed that the most serious problem limiting the addition of TCNE was the steric

176

hindrance. This limitation need to be considered before designing a new acetylenic polymer

precursor.

An extended it-conjugated TCBD NLO chromophore can be obtained from a thienyl

acetylene derivative. A low electronic absorption energy suggests that this longer n-

conjugated TCBD will be a very good candidate for a high |3 value chromophore. The

quantitative conversion of all three triple bonds of 4,4^4''-triethynyltriphenylamine into three

TCBD units has emphasized the remarkable efficiency of this reaction. The reaction of TCNE

with higher ionization energy substrates such as 4-ethynyl anisole and 4-cyanoethynyl-N,N-

dimethylaniline yields quite interesting anisole TCBD and PCBD providing more selections of

the acetylene substrates.

177

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ACKNOWLEDGMENTS

This dissertation could not have been completed without the inspiration and assistance

of many people. First I would like to thank Professor Thomas J. Barton for the great four

years and ten months I have spent in his research group. His style of teaching chemistry and

philosophy has always kept me looking forward to the group meeting times. With his

encouragement, support, and acquaintance, working in the lab has been as pleasant as

watching the Cyclones win the Big Eight final basketball tournament He will always be

greatly appreciated. I would also like to thank my committee members for devoting their time

and assistance.

I would like to express my appreciation to the members of Barton research group,

both past and present Especially, I would like to thank Dr. Sina Ijadi-Maghsoodi for his

technical advice and help; Mrs. Kathie Hawbaker, for her kind help on many occasions; Dr.

Yiwei Ding for his valuable discussion when I started my research; Mr. Nathan Classen and

Mr. Andrew Chubb for correcting the English of this thesis; and all the friends in our group for

their friendship and research discussion.

In addition, Professor Joseph Shinar, Dr. Andy V. Smith and other group members

from Department of Physics at ISU have contributed to the electroluminescence and optically

detected magnetic resonance studies of the polymers. I would like to thank Dr. Victor G.

Young, Jr. for the crystallographic results; Dr. Dave Scott and Dr. Karen Ann Smith for their

assistance in NMR spectroscopy; and Dr. Kamel Harrata and Mr. Charles Baker for mass

spectroscopic data.

190

I would also like to thank Mr. Kris E. Spence for being a great roommate during the

last three years in ISU. Besides his invaluable friendship, he has tremendously helped

correcting and improving my English through the years.

Finally, I would like to use this work to express my deep gratitude to my parents.

Their love, support and sacrifices throughout my education have been a main inspiration for

me.

Financial support for this work from the Director of Energy Research, Office of Basic

Energy Sciences of DOE, National Science Foundation is gratefully acknowledged.

This work was performed at Ames Laboratory under Contract No. W-7405-Eng-82

with the U.S. Department of Energy. The United States Government has assigned the DOE

Report number IS-T1777 to this thesis.